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To Design a Small Pneumatic Actuator Driven Parallel Link Mechanism for Shoulder Prostheses for Daily Living Use

Written By

Masashi Sekine, Kento Sugimori and Wenwei Yu

Submitted: 17 November 2010 Published: 29 August 2011

DOI: 10.5772/22050

From the Edited Volume

On Biomimetics

Edited by Assoc. Lilyana D. Pramatarova

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1. Introduction

Only in Japan, there are about 82,000 upper limb amputees (Ministry of Health, Labour and Welfare, 2005). Using upper limb prostheses could restore the function for them, thus improve significantly the quality of their activities of daily living [ADL]. Compared with below-elbow prostheses, shoulder prostheses are left behind in their development, due to high degrees of freedom [DOF] required, which demands a large number of actuators, thusdenotes a large size and a heavy weight, and complicated control mechanism.

Recently, there is a certain body of research on developing roboticdevices that could be used as prostheses for shoulder amputees (Jacobson et al., 1982; Motion Control, Inc., 2006-2011; The Johns Hopkins University Applied Physics Laboratory [APL], 2011; Troncossi et al., 2005, 2009a, 2009b). These research efforts have led to artificial prostheses with high functionality and performance.For example, the prosthetic arm of Defense Advanced Research Projects Agency and APL, has 25 DOFs, individual finger movements, dexterity that approaches that of the human limb, natural control, sensory feedback, and a number of small wireless devices that can be surgically implanted (or injected) to allow access to intramuscular signals(APL, 2011). The Utah Arm 3, a modification of the previous Utah Arm that has been the premier myoelectric arm for above elbow amputees, has two microcontrollers that are programmed for the hand and elbow,accordingly, allowing separate inputs and hence simultaneous control of both, and that is, the wearer can operate the hand and elbow concurrently for natural function (Jacobson et al., 1982; Motion Control, Inc., 2006-2011). The hybrid electric prosthesis for single arm amputee of Tokyo Denki University possesses a ball joint of 3 DOFs in humeral articulation. Patient operates the prosthesis to optional point by pressing a switch with the other healthy limb to free the joint, and releases to fix and hold the prosthetic arm stably (Nasu et al., 2001). Moreover, the electromechanical shoulder articulation with 2 DOFs for upper-limb prosthesis that has two actuated joints embedded harmonic drives, an inverted slider crank mechanism, and ball screw, has been developed (Troncossi et al., 2005, 2009a, 2009b).

These prostheseshave the following characteristics: they are more or less anthropomorphic, basically supported by metal frames or parts, driven by electric motors, therefore, many of them seem to be not suitable for the daily living use: they are not lightweight, not convenient, with a bad portability, and lack of backdrivability which could contribute to the safety use in daily living.

Using pneumatic actuators (Festo AG & Co. KG, 2002-2008; Folgheraiter & Gini, 2005), some researchers have developed sophisticated manipulators having structure similar to human upper limb. Employing pneumatic actuators that could naturally realize backdrivability, ensures safety against collisions or contact between the prosthetic shoulder and its environments around. In the Airic's_arm (Festo AG & Co. KG, 2000-2008), 30 artificial muscles were used to move the artificial bone structure comprising the ulna, radius, the metacarpal bones and the bones of the fingers, as well as the shoulder joint and the shoulder blade. The MaximumOne, a robot arm ofArtificial Intelligence and Robotics Laboratory, Politecnico di Milano, consists of two joints with 4 DOFs in all.The shoulder is made up of a ball joint with 3 DOFs and driven by five actuators, and the elbow is a revolute joint with 1 DOF and driven by two actuators (Folgheraiter & Gini, 2005).However, the manipulators are basically not for prosthetic use, moreover, they are not portable, especially due to the big air compressor.

This study aims to develop a lightweight shoulder prosthesis that could be easily fitted to and carried by amputees, therefore a convenient one.This chapter presents kinematical analysis, procedure for finding optimal configurations for the prosthetic arm, and verification of the design concepts.

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2. Design concepts

A shoulder prosthesis for daily living use should be light-weight, portable, and safe. Consideration to design such a shoulder prosthesis is described as follows.

  1. Using small pneumatic actuators driven by small portable air compressor for weight saving and portability. To meet portability and light-weight requirements, small actuators and compressors are musts for shoulder prostheses. The pneumatic actuators Sik-t, Sik-t Power-Type (Squse Inc.: 1g, 20N; 3g, 130N), air compressors MP-2-C (Squse Inc.: 180g, 0.4 MPa) are products developed recently for robotic application with light-weight and good portability. In this research, these products were employed as actuators and their air sources. The purpose of this research is to design shoulder prostheses with optimal spatial functionality using these actuators.

  2. Employing a parallel link mechanism to enable high rigidity and high torque output. The natural viscoelasticity of pneumatic actuators could contribute to backdrivability, and safety of shoulder prostheses, however, it also affects the payload of the system. Moreover, since small actuators have a limited tensile force, a structure that could exert high torque output is preferable. That is why a parallel link mechanism that could improve structural rigidity was employed. However, the parallel link structure usually has a limited stretch along axial direction. The working space of the prostheses should be adjusted to fit individual users’ expected frequently accessed area [EFAA]. To the best of our knowledge, there are no investigation results reported on how to match working space of end-effector to EFAA of individual users’ hand. This is the main objective of this study.

  3. Using a rubber backbone for the parallel link mechanism to enable trade-off between working space and payloads. Since, the parallel link structure usually has a limited stretch along axial direction. A flexible backbone for the parallel link could give more possibility to deal with the trade-off between payloads and working space, however, this raises one more design variable, which should also be carefully investigated in the design process. This is an on-going research theme, and will be addressed in other papers.

  4. Designing a special backpack that could contain the shoulder prostheses and all accessories, and could be worn by the amputee user himself with minimal effort. This needs the shoulder prosthesis be foldable, and the backpack be designed for conveniently getting the shoulder prosthesis in and out. This will be approached in the next stage and addressed in other papers. The ultimate goal of this study is to build a shoulder prosthesis that could be used in daily living by shoulder amputees. The purpose of this paper is to describe the structure of the prosthesis, and approach to find optimal configurations based on the aforementioned design consideration. Fig. 1 shows an illustration of the shoulder prosthetic system, which is drafted with computer aided design [CAD] software SolidWorks (Dassault Systèmes SolidWorks Corp.) and human body model from HumanWorks software (zetec, Ltd.)

The remainder of this chapter is organized as follows. At first, in section 3, the basic structure of the prosthesis was described and several formulae for kinematics and statics of it were derived for further analysis. After that, the way to achieve the spatial accessibility and manipulability was explained in section 4. Then several experimental results concerning the design of the prosthesis were shown with discussion. Following that, a conclusion was given based on the results and discussion.

Figure 1.

The shoulder prosthetic system.

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3. Kinematics and statics

To decide the physical dimension of the shoulder prosthesis, both the kinematics, statics of the prosthesis and the spatial configuration, expected frequently accessed area [EFAA] of users’ hand should be considered. In this section, the kinematics and statics of the proposed shoulder prosthesis were derived for further analysis. Several estimative indexes were also defined to compare different potential solutions, thus to decide physical dimensions (configuration) of the shoulder prosthesis. As described before, only the arm structure was modelled and analyzed, whereas the prosthesis with hand, the backpack, and the connection between arm structure and backpack were left for further studies.

3.1. Arm structure

The details of the arm structure (in the following explanation, denoted as the Arm) are shown in Fig. 2. The Arm is composed of three segments. Segment 1 links two disks called the Base 1 and the Platform 1 with the Backbone 1 and three pneumatic actuators, placed equiangularly with respect to the center of the Base 1. The Backbone 1 is fixed to the center of the Base 1, and connected to the center of the Platform 1 with two passive revolute joints. To simplify the analysis, the Backbone 1 was assumed as a compression spring that can only move along longitudinal direction, but not as a rubber rod as described in the design concept section. By assembling Base 1 and Platform 1 with a compressed Backbone 1, actuators and wires that connect the pneumatic actuators with two disks are constantly loaded. This allows the Platform 1 to move along the longitudinal direction of the Backbone 1, turn around the joint of Platform 1 and Backbone 1, as a result of length changes of the three actuators.

The Platform 1 disk of Segment 1 is also used as the Base 2 disk of the Segment 2, which has a similar structure with the Segment 1, but with a different length. Segment 3 contains only a rigid rod (Rod) fixed to the center of outside the Platform 2, i.e. the Base 3 of the Segment 3. For the convenience of description, let h 1, h 2 and l R be the initial length of the Backbone 1, 2 and Rod respectively.

Figure 2.

The structure of the Arm.

3.2. Kinematics

In order to analyze the behavior of end-effector and working space of the Arm, forward and inverse kinematics model of the parallel link mechanism were derived.

The coordinate system of the Arm is shown in Fig. 3. Without loss of the generality, the thicknesses of all disks, and the shaft diameters of Backbone 1, 2, Rod were set to 0. The global coordinate system O B1-XYZ is located at the center of the Base 1, with the Z-axis directed along the Backbone 1. The contact points of three pneumatic actuators to Base 1 (B 11 , B 12 , B 13) were aligned equiangularly along the peripheral of a circle with a radius r B , and B 11 is on the X-axis.

The local coordinate system O P1-x P1 y P1 z P1 locates at the center of disk Platform 1, h 1 away from O B1along the Z-axis. The contact points of pneumatic actuators to Platform 1 (P 11 , P 12 , P 13) are on radius r P . In turn, the contact points of three pneumatic actuators to Base 2 (B 21 , B 22 , B 23) are equiangularly set on circumference of a circle, radius r B , and B 21is on the x P1-axis. The local coordinate systemO P2 -x P2 y P2 z P2 is set at the center of Platform 2, and the distance from O P1is h 2. The contact points (P 21 , P 22 , P 23) are aligned equiangularly along the peripheral of a circle with a radius r P , and P 21 is on the x P2-axis.

Finally, the Rod of length l R is fixed up at O P2 along the z P2-axis.

Suppose the actuators are activated, and their lengths change (expressed discretely: l i gets to l i , i =1,..., 6). Therefore, h 1 and h 2 are converted to h 1 and h 2 , two passive joints (Joint 1) of Platform 1 and the one (Joint 2) of Platform 2 rotate by α,β, γ, σ (see Fig. 2, 3), respectively.

Figure 3.

Geometry of the parallel link arm.

At first, the position of O P1, P 1i ,P 1i ’(i=1, 2, 3)andthe rotation matrix R 1 of Joint 1 in O P1-x P1 y P1 z P1, i.e. P1 O P1, P1 P 1i , P1 P 1i ’ and P1 R 1 can be presented as follows:

O P 1 P 1 : (0, 0, 0),    P P 1 1 1 : ( r P , 0, 0),    P P 1 1 2 : ( - 1 2 r P ,   3 2 r P , 0),    P P 1 1 3 : ( - 1 2 r P , - 3 2 r P , 0) R P 1 1 = ( 1 0 0 0 c o s α s i n α 0 s i n α c o s α ) ( c o s β 0 s i n β 0 1 0 s i n β 0 c o s β ) = ( c o s β 0 s i n β sin α sin β cos α s i n α c o s β cos α sin β sin α cos α cos β )   E1

And,

P P 1 1 i ' = R P 1 1 P P 1 1 i ( i = 1,2,3) E2

Therefore, the coordinate of each element of P1 P 1i ’ is:

P P 1 1 1 ' : ( r P cos β r P sin α sin β r P cos α sin β ) P P 1 1 2 ' : ( 1 2 r P cos β 1 2 r P sin α sin β + 3 2 r P cos α 1 2 r P cos α sin β + 3 2 r P sin α  ) P P 1 1 3 ' : ( 1 2 r P cos β 1 2 r P sin α sin β 3 2 r P cos α 1 2 r P cos α sin β 3 2 r P sin α ) E3

Next, P 1i ’, B 1i ’in O B1-XYZ, i.e. B1 P 1i ’ and B1 B 1i ’ can be defined as:

B B 1 1 1 : ( r B , 0, 0),    B B 1 1 2 : ( 1 2 r B 3 2 r B , 0),    B B 1 1 3 : ( 1 2 r B 3 2 r B , 0) P B 1 1 i ' = P P 1 1 i ' + ( 0, 0,  h 1 ' ) T ( i = 1,2,3) E4

So, each element of B1 P 1i ’ can be expressed as:

P B 1 1 1 ' : ( r P cos β r P sin α sin β , - r P cos α sin β + h 1 ' ) P B 1 1 2 ' : ( 1 2 r P cos β 1 2 r P sin α sin β + 3 2 r P cos α 1 2 r P cos α sin β + 3 2 r P sin α + h 1 '  ) P B 1 1 3 ' : ( 1 2 r P cos β 1 2 r P sin α sin β 3 2 r P cos α 1 2 r P cos α sin β 3 2 r P sin α + h 1 ' ) E5

Accordingly, the length of each actuator can be defined:

l i ' = P B 1 1 i ' B B 1 1 i ¯ ( i = 1,2,3) E6

By Equation (5), (7) and (8), the equations describing the relation between the lengths of pneumatic actuators, wires attached in Segment 1, Backbone 1, and the angles of two revolute joints can be defined as follows:

( l 1 ' ) 2 = ( r P cos β - r B ) 2 + ( r P sin α sin β ) 2 + ( - r P cos α sin β + h 1 ' ) 2 E7
( l 2 ' ) 2 = ( 1 2 r P cos β + 1 2 r B ) 2 +   ( 1 2 r P sin α sin β + 3 2 r P cos α 3 2 r B ) 2          + ( 1 2 r P cos α sin β + 3 2 r P sin α + h 1 ' ) 2 E8
( l 3 ' ) 2 = ( 1 2 r P cos β + 1 2 r B ) 2 +   ( 1 2 r P sin α sin β 3 2 r P cos α + 3 2 r B ) 2          + ( 1 2 r P cos α sin β 3 2 r P sin α + h 1 ' ) 2 E9

Equation (9) is a simultaneous equation with three unknown variables, α,β,h 1’. In the case that the lengths l 1’, l 2’, l 3’ are given, it is possible to calculate α,β,h 1’ by using the Newton method (Ku, 1999; Merlet, 1993; Press et al., 1992). Similarly, for the Segment 2 (i.e. in O P1-x P1 y P1 z P1), the following equation can be derived. In the case that the length l 4’, l 5’, l 6’, are given, it is possible to calculate γ, σ,h 2’.

( l 4 ' ) 2 = ( r P cos σ r B ) 2 + ( r P sin γ sin σ ) 2 + ( r P cos γ sin σ + h 2 ' ) 2 ( l 5 ' ) 2 = ( 1 2 r P cos σ + 1 2 r B ) 2 +   ( 1 2 r P sin γ sin σ + 3 2 r P cos γ 3 2 r B ) 2          + ( 1 2 r P cos γ sin σ + 3 2 r P sin γ + h 2 ' ) 2 ( l 6 ' ) 2 = ( 1 2 r P cos σ + 1 2 r B ) 2 +   ( 1 2 r P sin γ sin σ 3 2 r P cos γ + 3 2 r B ) 2          + ( 1 2 r P cos γ sin σ 3 2 r P sin γ + h 2 ' ) 2 E10

The position of the Rod end P RE ’ in O P2 -x P2 y P2 z P2, i.e. P2 P RE ’ can be defined as:

P P 2 R E ' = ( 0 , 0 , l R ) T E11

Let x, y, z be the coordinate of B1 P RE ’, then end position of the Rod, x, y, z in O B1-XYZ can be described as:

( x y z ) T = R P 1 1 ( R P 2 2 P P 2 R E ' + O P 1 P 2 ' ) + O B 1 P 1 ' ( x y z ) = ( c o s β 0 s i n β sin α sin β cos α s i n α c o s β cos α sin β sin α cos α cos β ) [ ( c o s σ 0 s i n σ sin γ sin σ cos γ s i n γ c o s σ cos γ sin σ sin γ cos γ cos σ ) ( 0 0 l R ) + ( 0 0 h 2 ' ) ] + ( 0 0 h 1 ' ) E12

3.3. Jacobian matrix

In order to evaluate the motion characteristics of the Arm, it is necessary to develop theJacobian matrix of the Arm structure.

As l i ’(i=1, ,6), α,β,h 1’, γ, σand h 2’ can be taken as functions of time t, noticing l i ’,x, y, zare functions of α,β,h 1’, γ, σ, h 2’, the Equation (9), (10), (12) can be differentiated with respect to t, to get the following equations. The A, B, Care the matrixes with element a ij , b ij (i,j=1,2,3), c ij (i=1,2,3, j=1, , 6), respectively.

( l 1 ' l 2 ' l 3 ' ) = ( a 1 1 a 1 2 a 1 3 a 2 1 a 2 2 a 2 3 a 3 1 a 3 2 a 3 3 ) ( α β h 1 ' ) = A ( α β h 1 ' ) , ( l 4 ' l 5 ' l 6 ' ) = ( b 1 1 b 1 2 b 1 3 b 2 1 b 2 2 b 2 3 b 3 1 b 3 2 b 3 3 ) ( γ σ h 2 ' ) = B ( γ σ h 2 ' ) , E13
( x y z ) = ( c 1 1 c 1 2 c 1 3 c 1 4 c 1 5 c 1 6 c 2 1 c 2 2 c 2 3 c 2 4 c 2 5 c 2 6 c 3 1 c 3 2 c 3 3 c 3 4 c 3 5 c 3 6 ) ( α β h 1 ' γ σ h 2 ' ) = C ( α β h 1 ' γ σ h 2 ' ) E14

Next, the orientation of B1 P RE ’ in O B1-XYZ can be expressed by Equation (15), where the element of the matrix P1 R 1 P2 R 2 is presented by r ij (i,j=1,2,3).

R P 1 1 R P 2 2 = ( c o s β 0 s i n β sin α sin β cos α s i n α c o s β cos α sin β sin α cos α cos β ) ( c o s σ 0 s i n σ sin γ sin σ cos γ s i n γ c o s σ cos γ sin σ sin γ cos γ cos σ ) = ( r 1 1 r 1 2 r 1 3 r 2 1 r 2 2 r 2 3 r 3 1 r 3 2 r 3 3 ) E15

By using Equation (15), the Euler angles (ϕ,θ, ψ) can be acquired (Yoshikawa, 1988).

φ = a t a n 2 ( r 2 3 , r 1 3 ) , θ = a t a n 2 ( ( r 1 3 ) 2 + ( r 2 3 ) 2 , r 3 3 ) , ψ = a t a n 2 ( r 3 2 , r 3 1 ) (0 θ π ) E16

Equation (17) can be derived by differentiating Equation (16) with regard to time t (Yoshikawa, 1988):

φ = ( r 23 ) r 1 3 r 2 3 ( r 13 ) ( r 2 3 ) 2 + ( r 1 3 ) 2 , θ = ( ( r 1 3 ) 2 + ( r 2 3 ) 2 ) r 3 3 ( r 1 3 ) 2 + ( r 2 3 ) 2 ( r 33 ) ( r 1 3 ) 2 + ( r 2 3 ) 2 + ( r 3 3 ) 2 , ψ = ( r 32 ) r 31 + r 32 ( r 31 ) ( r 32 ) 2 + ( r 31 ) 2 (0 θ π ) E17

ϕ,θ, ψ are functions of α,β, γ, σ. Therefore, by using a matrix D with element d ij (i=1, 2, 3, j=1, 2, 4, 5), (ϕ,θ, ψ) T can be expressed as:

( φ θ ψ ) = ( d 1 1 d 1 2 0 d 1 4 d 1 5 0 d 2 1 d 2 2 0 d 2 4 d 2 5 0 d 3 1 d 3 2 0 d 3 4 d 3 5 0 ) ( α β h 1 ' γ σ h 2 ' ) = D ( α β h 1 ' γ σ h 2 ' ) E18

Equation (14) and (18) can be integrated to the following equation.

( x y z φ θ ψ ) = ( C D ) ( α β h 1 ' γ σ h 2 ' ) E19

Let inverse matrix of A and B be A -1 and B -1, which comprise elements a -1 ij , b -1 ij (i,j=1,2,3), then α,β,h 1’, γ, σ, h 2’can be derived from Equation (13).

( α β h 1 ' ) = A 1 ( l 1 ' l 2 ' l 3 ' ) = ( a 1 11 a 1 12 a 1 13 a 1 21 a 1 22 a 1 23 a 1 31 a 1 32 a 1 33 ) ( l 1 ' l 2 ' l 3 ' ) , ( γ σ h 2 ' ) = B 1 ( l 4 ' l 5 ' l 6 ' ) = ( b 1 11 b 1 12 b 1 13 b 1 21 b 1 22 b 1 23 b 1 31 b 1 32 b 1 33 ) ( l 4 ' l 5 ' l 6 ' ) , ( α β h 1 ' γ σ h 2 ' ) = ( A 1 0 0 B 1 ) ( l 1 ' l 2 ' l 3 ' l 4 ' l 5 ' l 6 ' ) E20

Therefore, by using Equation (19) and (20), the vector representing the posture of end-effector can be acquired.

( x y z φ θ ψ ) = ( C D ) ( α β h 1 ' γ σ h 2 ' ) = ( C D ) ( A 1 0 0 B 1 ) ( l 1 ' l 2 ' l 3 ' l 4 ' l 5 ' l 6 ' ) = ( c 1 1 c 1 2 c 1 3 c 1 4 c 1 5 c 1 6 c 2 1 c 22 c 23 c 24 c 25 c 26 c 3 1 c 32 c 33 c 34 c 35 c 36 d 1 1 d 1 2 0 d 1 4 d 1 5 0 d 2 1 d 22 0 d 24 d 25 0 d 3 1 d 32 0 d 34 d 35 0 ) ( a 1 1 1 a 1 1 2 a 1 1 3 0 0 0 a 1 2 1 a 1 22 a 1 23 0 0 0 a 1 3 1 a 1 32 a 1 33 0 0 0 0 0 0 b 1 1 1 b 1 1 2 b 1 1 3 0 0 0 b 1 2 1 b 1 22 b 1 23 0 0 0 b 1 3 1 b 1 32 b 1 33 ) ( l 1 ' l 2 ' l 3 ' l 4 ' l 5 ' l 6 ' ) = J 1 ( l 1 ' l 2 ' l 3 ' l 4 ' l 5 ' l 6 ' ) E21

From the above equation, the Jacobian matrixJ 1 can be calculated.

3.4. Static mechanics

Let force generated and virtual displacement of each actuator be τ andΔl, and the force generated and virtual displacement of Rod end P RE ’ be F and Δx. From virtual work principle, the relationship between these two pairs is:

F T Δ x = τ T Δ l E22

By using Equation (21)

Δ x = J 1 Δ l , J 1 1 Δ x = Δ l , Δ l = J Δ x ( J = J 1 1 ) E23

Therefore, from Equation (22) and (23), the relation between F and τis acquired.

F T Δ x = τ T J Δ x , F T = τ T J , ( F T ) T = ( τ T J ) T F = J T τ E24
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4. Method of analysis

In this section, an evaluation index based on the Jacobian Matrix is presented, and the process to evaluate possible configurations, i.e., the physical dimension of the shoulder prosthesis is described.

4.1. An estimative index of manipulability: condition number

The condition number (Arai, 1992) was employed as evaluation indicator for the motion characteristics of the Arm mechanism. The condition number is based on the singular value of the Jacobian matrix. The Equation (24) can be described as the expression for how τis convertedinto F. Furthermore, a singular value decomposition, expressed by Equation (25), can make the property of Jeven clearer.

J T = U Σ V T E25

Here, Uand V are 6x6 orthogonal matrixes, which can be described by Equation (26).

U = ( u 1 , , u 6 ) T , V = ( v 1 , , v 6 ) T , Σ = d i a g ( σ 1 , , σ 6 ), ( σ 1 σ 2 σ 6 0 ) E26

Substituting Equation (25) into (24), the relation between τand F can be rewritten as Equation (27).

F = U Σ V T τ , U T F = Σ V T τ E27

Equation (26) and (27) can be rewritten using the elements of Uand V.

u i T F = σ i v i T τ E28

Considering the function of the manipulator, it is preferable that the forces that could be generated at the end of the Rod in all direction are as uniform as possible. That is, it is the ratio of the maximum singular value to the minimum one, i.e., the condition number, should be close to 1 as much as possible.

Since the condition number of J T reflects the both the forceand torque working at the end of the Rod, in order to conduct proper evaluations, it is necessary to separate the influence of forceand torque. Therefore, in the Equation (24), J T is separated into the part contributing to the force and the one contributing to the torque, and singular value decomposition was conducted at two parts separately. Therefore, J T is separated as follows.

J T = [ J f T J m T ] E29

Here,J f T andJ m T are 3x6 matrixes, so, three singular values σ fi , σ mi (i=1,2,3) exist in each of J f T and J m T . Thus, we use the following three condition numbers as estimative index:

C = σ 1 σ 6 C f = σ f 1 σ f 3 C m = σ m 1 σ m 3 E30

4.2. An outline of the evaluation process

The following is an outline of the evaluation process.

  1. Setting up a coordinate space Σ CS1;

  2. Setting up an initial configuration (physical dimension of the Arm mechanism), and modelling the Arm and human body in Σ CS1;

  3. Defining EFAA (Expected Frequently Accessed Area) and RA (Reachable Area) of the Arm in Σ CS1;

  4. For different length of pneumatic actuators, reflecting translational motion of the actuators, numerically calculating andplotting the Rod end positionP RE ’;

  5. Calculating the estimative indexes for all the P RE ’ in EFAA and RA;

  6. Changing the parameters of the Arm mechanism, and going back to recalculating Step 4;

  7. After a certain number of loops of execution (Step 4 to 6), evaluating all the configurations to decide configurations optimal for the spatial accessibility (plot number in EFAA) and manipulability.

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4.3 Modelling the Arm and human body in the coordinate space

A 3D human body model software (HumanWorks) was used for the above-mentioned human body. This HumanWorks model, shown in Fig. 4, 167.0 centimeters tall, is a 50th percentile model of Japanese male based on Japanese Industrial Standards.

Fig. 5(a) shows the coordinate system, Σ CS1, for the shoulder prosthetic system. It presents not only the geometry of the Arm, and also the EFAA, and their relationship.

As illustrated in the Fig. 5(a), the point of origin is set at the intersection of the median sagittal plane(Y=0), with the horizontal plane(X=0) and the coronal plane(Z=0) passing through the acrominon. Positions of the acrominon are assumed as (0, ±170, 0). In Fig. 5(c), (d), the size of some parts of human body is presented. Considering the shape and positional relationships of the shoulder, neck, head and the Arm, the Base 1 of the Arm is set at (-80, 150, 0), the axis direction of O B1-XYZ (see Fig. 3) is set to conform to the Z axis of the Σ CS1. Moreover, based on the arm size of the 50th percentile model, we estimated the size of the Arm suitable for the human body, and setup initial values for the physical dimension of the Arm (Fig. 5(b)). These initial values, which constitute an initial configuration, are summarized as follows (see Fig. 3 for the meanings of the symbols).

Figure 4.

A 3D human body model of HumanWorks.

h 1 = 100 h 2 = 170 l R = 250 r B = 50 r P = 45 (mm) E31

Figure 5.

The coordinate system Σ CS1 and the HumanWorks model.

4.4. Important areas in the working space of the Arm

Two important areas in the working space of the Arm are defined for the analysis and evaluation of the Arm. One is the area close to the chest and the median sagittal plane, which is expected to be accessed very frequently during most daily living tasks. This area is the EFAA defined before, and expressed as Σ EFAA . Another is the area that represents the reachable area [RA] of the end effector, defined as Σ RA . Geometries of Σ EFAA and Σ RA are illustrated as in Fig. 6. The volumes of Σ EFAA and Σ RA are set to 12000cm3 and 75000cm3, respectively.

Figure 6.

Geometries of the areas Σ EFAA and Σ RA .

4.5. Calculation and analysis

All the calculation was calculated numerically by using Matlab (MathWorks, Inc.). A simplified Arm, as shown in Fig. 7, is drawn for visualization in Matlab. P RE ’ is calculated by substituting the initial values to Equation (12), with variable length of actuators, which stands for the translational motion of the pneumatic actuators. Three different values were set for each l i (i=1, ,6) in Fig. 3(b). Supposing that the resting length of the actuators are LW i (i=1, ,6), and the maximum,minimum, middle increment of the actuators are L max , L min , L mid , then the three different values are LW i + L max , LW i + L min , LW i +L mid  (Fig. 8). Thus, for each Arm configuration, a total number of 36=729 sets of calculation were calculated for P RE ’, then the configuration could be evaluated.

Figure 7.

Models with Matlab.

Figure 8.

Three different values of l i .

The estimative index described in section 4.1 was adapted as follows, for evaluating different aspects of the system.

  • N EFAA : Number of points plotted in Σ EFAA (Spatial accessibility)

  • N RA : Number of points plotted in Σ RA (Spatial accessibility)

  • M t (C): 15percent trimmed mean condition number C (Eq. 30) of points plotted in Σ EFAA (Manipulability)

  • M t (C f ): 15percent trimmed mean condition number C f (Eq. 31) of points plotted in Σ EFAA (Manipulability)

  • M t (C m ): 15percent trimmed mean condition number C m (Eq. 32) of points plotted in Σ EFAA (Manipulability)

After the calculation and evaluation, the physical dimensions of the Arm structure were changed, and the calculation and evaluation for the new configuration were repeated. Note, in this chapter, only the results of changing h 2 and l R are to be reported.

From this process, optimal configurations of the Arm structure could be determined.

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5. Results

5.1. Results of the initial configuration

A plot of P RE ’ for the Arm structure with the initial configuration is shown in Fig. 9, where points in red, blue and gray stand for the P RE ’ located in Σ EFAA , in Σ RA and outside of the both areas, respectively. Basically, the group of points is longitude-axis-symmetric.

Figure 9.

Plotting P RE ’ with the initial parameter.

Table 1 shows the values of estimative indexes defined in section 4.5

NEFAA NRA Mt(C) Mt(Cf) Mt(Cm)
68 393 852240 279.41 1195.5

Table 1.

Estimative index with the initial parameter.

5.2. Results of other configurations generated by changing parameters

Suppose that the parameters h 2 and l R are changed as in Equation (34), where, beginning with 170mm, 250mm (parameters of the initial configuration) h 2 and l R increase or decrease incrementally by 25mm and 50mm, respectively, and i is an integer, taking value 0, 1, 2.

h 2 = 170 ± 25 i l R = 250 ± 50 i ( i = 0,1,2) (mm) E32

Therefore, a total number of 25 combinations could be made, and identified with No.1-1, , No.1-25, as shown in Table 2. The estimative indexes were calculated for all the combinations. The N EFAA and N RA are shown in Fig. 10. The horizontal axis stands for the ID of combination, and vertical axis represents N EFAA (Fig. 10(a)) or N RA (Fig. 10(b)).

NO.1- 1 2 3 4 5 6 7 8 9 10 11 12 13
h 2(mm) 120 145 170 195 220 120 145 170 195 220 120 145 170
lR (mm) 150 150 150 150 150 200 200 200 200 200 250 250 250
NO.1- 14 15 16 17 18 19 20 21 22 23 24 25
h 2(mm) 195 220 120 145 170 195 220 120 145 170 195 220
lR (mm) 250 250 300 300 300 300 300 350 350 350 350 350

Table 2.

Combinations of h 2and l R .

Fig. 10(b) shows a tendency that as the Arm length l R gets longer, N RA decreases almost monotonically, but there is a steep descent after No.1-21.This can be attributed to the fact that a certain Arm length l R would make the Rod end more likely to go over the Σ RA .

Figure 10.

N EFAA and N RA of 25 combinations of h 2, l R .

Whereas, as shown in Fig. 10(a), there are roughly two stages. In the stage after No. 1-13, N EFAA decreases while vibrating irregularly and strongly. This can be attributed to the reason same as before: a certain Arm length l R would make the Rod end more likely to go over the Σ EFAA . A different point is that the value of No. 1-16, with a smallest h 2 (h 2 = 120mm), shows a large local maximum. It seems h 2 affected N EFAA more than N RA . In the stage before No.1-12, N EFAA gradually increases as the Arm length gets longer, which means that it is necessary to precisely investigate the possibility of the Arm with shorter length, i.e., smaller l R and h 2. Thus, the Arm with the parameters shown in Equation (33) was investigated.

h 2 = 100 + 7 i l R = 70 + 20 i ( i = 0, , 9) (mm) E33

A total number of 100 combinations could be made, and identified with No.2-1, , No.2-100, as shown in Table 3. The estimative index was calculated for all the combinations. The results are shown in Table 3 and Fig. 11, 12.

NO.2- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 70 70 70 70 70 70 70 70 70 70 90 90 90 90 90 90 90 90 90 90
NO. 2- 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 110 110 110 110 110 110 110 110 110 110 130 130 130 130 130 130 130 130 130 130
NO. 2- 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 150 150 150 150 150 150 150 150 150 150 170 170 170 170 170 170 170 170 170 170
NO. 2- 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 190 190 190 190 190 190 190 190 190 190 210 210 210 210 210 210 210 210 210 210
NO. 2- 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 230 230 230 230 230 230 230 230 230 230 250 250 250 250 250 250 250 250 250 250

Table 3.

Combinations of h 2and l R .

As shown in Fig. 11, within the range, as the Arml R gets longer, N EFAA and N RA changes in the opposite direction: N EFAA increases and N RA decreases. Thus, it is reasonable that, prospective solution for the Arm should be specified within this range.

In Fig. 12, the horizontal axis stands for the ID of combination, and vertical axis represents M t (C) (Fig. 12(a)), M t (C f ) (Fig. 12(b))and M t (C m ) (Fig. 12(c)). There is a steep increase between No. 2-87 and No. 2-88. Since, the smaller value of M t (C), M t (C f ) and M t (C m ) means the better manipulability of the shoulder prosthesis, prospective solutions should be chosen from the combinations before the No. 88.

Apparently, better accessibility requires a bigger value of N EFAA and N RA, however, from the aforementioned results, it is clear that within the range investigated (as shown in Fig. 11), they can not be satisfied simultaneously. That is, N EFAA and N RA should be traded-off depending on which area (EFAA or RA) is more important.

For this purpose, thresholds were determined as follows to reflect different weighting policies and the constraint from manipulability, i.e., M t(C), M t(C f), M t(C m). The average μ 0and standard deviation σ 0 of N EFAA, N RA, M t(C), M t(C f), M t(C m) were calculated. For M t(C), M t(C f), M t(C m), threshold value was set as μ 0+0.5σ 0, which stands for the largest mean value that could be allowed. IN the EFAA-favoured policy, N EFAA should be larger than μ 0+0.5σ 0(upper bound), but N RA should be at least larger than μ 0-0.5σ 0 (lower bound). Similarly, in the RA-favoured policy, N RA should be larger than μ 0+0.5σ 0, but, N EFAA should be at least larger than μ 0-0.5σ 0. Equation (34)-(a) and (b) show the threshold values reflecting the EFAA-favoured and RA-favoured policies, respectively.

Figure 11.

N EFAA and N RA of 100 combinations of h 2, l R .

Figure 12.

M t (C), M t (C f ) and M t (C m ) of 100 combinations of h 2, l R .

N E F A A 48 .43 N R A 480 .16 M t ( C ) 232709 .74 M t ( C f ) 113 .18 M t ( C m ) 363 .05 } (a)      or       N E F A A 28 .97 N R A 559 .78 M t ( C ) 232709 .74 M t ( C f ) 113 .18 M t ( C m ) 363 .05 } (b)  E34

By using the Equation (34), 8 configuration candidates were selected. In Table 4, the configurations painted red and blue are selected by Equation (34)-(a) and Equation (34)-(b), respectively.

Furthermore, since M t (C), M t (C f ), M t (C m ) are the mean values for C, C f , C m , for the configurations selected by the threshold values shown in the Equation (34), there is a possibility that, at some postures, the manipulability might be extremely bad. Therefore, it is necessary to specify the lower bound for the worst manipulability that could be allowed. The following three additional estimative indexes were defined, which means the configuration with a smaller 3rd quartile (the value of a point that divides a data set into 3/4 and 1/4 of points) would be tolerated. They are only defined for EFAA, because this area requires precise manipulation more than RA.

  • Q 3(C): the 3rd quartile of C (Eq. 30) of points in Σ EFAA

  • Q 3(C f ): the 3rd quartile of C f (Eq. 31) of points in Σ EFAA

  • Q 3(C m ): the 3rd quartile of C m (Eq. 32)of points in Σ EFAA

NO. 2- 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 70 70 70 70 70 70 70 70 70 70 90 90 90 90 90 90 90 90 90 90
NEFAA 3 3 5 6 8 10 10 13 15 18 8 8 11 12 12 16 17 17 24 25
NRA 666 663 657 643 637 634 622 618 616 614 641 633 627 621 615 614 608 602 600 590
Mt(C) 50704 56269 41798 61809 62402 80493 87778 98844 112960 103360 45231 50546 60187 82503 90626 75898 93985 101570 77448 80410
Mt(Cf ) 79.25 84.21 58.91 87.39 90.53 109.30 114.93 119.21 130.85 114.79 70.65 75.55 83.15 106.78 112.58 89.04 105.86 110.83 77.06 77.25
Mt(Cm ) 228.61 253.73 185.23 277.29 255.36 340.25 368.36 387.89 485.79 452.91 136.36 155.24 184.67 256.05 282.46 242.75 325.68 352.09 278.81 289.48
NO. 2- 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 110 110 110 110 110 110 110 110 110 110 130 130 130 130 130 130 130 130 130 130
NEFAA 12 14 16 16 19 22 25 27 29 32 24 24 28 30 30 31 35 35 39 41
NRA 617 615 605 601 601 592 582 578 576 570 599 591 577 571 569 560 552 540 526 518
Mt(C) 48855 47609 62863 69071 77982 71438 68962 70028 71026 98448 53563 58893 68692 70595 76635 80551 70878 76154 86355 88802
Mt(Cf ) 66.87 61.58 76.17 80.51 86.47 72.17 67.07 65.98 64.83 92.55 65.19 69.58 73.46 72.99 77.12 78.90 63.64 66.64 77.58 78.17
Mt(Cm ) 113.31 114.71 156.27 173.98 215.79 201.13 196.84 207.91 212.25 311.08 115.32 129.50 164.08 171.75 188.88 201.24 175.38 190.43 225.62 232.43
NO. 2- 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 150 150 150 150 150 150 150 150 150 150 170 170 170 170 170 170 170 170 170 170
NEFAA 30 31 31 33 33 37 42 44 46 47 39 40 41 43 44 45 46 47 50 50
NRA 562 556 548 544 536 521 521 517 511 509 532 528 522 518 518 515 513 503 495 489
Mt(C) 89754 94852 68424 70380 76201 78502 82345 85105 91295 87927 61794 65769 69759 86706 91159 95923 100940 93368 94581 100830
Mt(Cf ) 60.51 62.76 66.86 66.84 70.64 70.61 69.04 69.80 70.50 62.70 44.06 45.93 47.52 58.05 59.97 62.17 64.21 57.00 57.09 59.57
Mt(Cm ) 178.42 192.94 134.79 141.66 156.08 164.88 184.89 194.87 218.37 212.98 105.68 115.80 126.23 154.23 166.32 177.94 192.08 188.33 193.69 208.67
NO. 2- 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 190 190 190 190 190 190 190 190 190 190 210 210 210 210 210 210 210 210 210 210
NEFAA 41 42 43 43 45 48 48 49 52 52 44 45 46 48 50 50 50 53 54 56
NRA 514 514 504 498 482 475 459 445 439 429 474 460 454 444 446 437 429 425 423 419
Mt(C) 64195 82381 87069 93562 96117 85546 91649 95965 97942 104230 126780 133450 140020 117990 121270 129470 137990 139560 145390 149270
Mt(Cf ) 42.13 52.51 54.78 58.05 58.98 51.23 53.77 55.19 55.33 57.74 65.96 68.55 71.19 61.53 62.54 65.91 69.30 69.33 71.23 72.07
Mt(Cm ) 92.34 116.28 128.30 141.54 149.27 144.18 157.25 167.21 174.10 187.66 167.59 183.12 197.12 170.24 180.53 196.54 213.14 219.68 231.90 241.78
NO. 2- 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100
h 2(mm) 100 107 114 121 128 135 142 149 156 163 100 107 114 121 128 135 142 149 156 163
lR (mm) 230 230 230 230 230 230 230 230 230 230 250 250 250 250 250 250 250 250 250 250
NEFAA 58 58 58 57 57 62 62 65 67 67 67 67 70 69 71 71 74 74 75 73
NRA 434 434 428 420 424 419 417 415 411 411 422 418 414 414 414 409 405 405 401 393
Mt(C) 90894 97221 103940 109450 116780 149070 158490 359530 357440 381760 296780 325030 600120 654050 690430 749300 617550 665350 703810 753910
Mt(Cf ) 44.48 47.42 50.40 54.04 57.11 69.18 72.59 141.36 132.40 139.36 118.09 127.62 231.17 242.59 251.72 268.34 218.07 231.35 241.08 254.22
Mt(Cm ) 107.26 118.82 131.14 139.62 152.66 199.98 216.74 487.80 502.54 546.75 280.27 321.11 672.03 770.05 845.97 951.96 783.71 868.60 942.70 1034.10

Table 4.

Combinations of h 2and l R .

Fig. 13 shows the values of the new estimative indexes Q 3(C), Q 3(C f ) and Q 3(C m ) for 100 configurations listed in Table 4. Q 3(C m ) oscillated with a gradually decreasing peak-to-peak value. Q 3(C), Q 3(C f ) oscillated, with a biggest peak-to-peak value of 20000, and 250 respectively, and turned to stable at a comparatively low level between No.2-50 to No.2-70. Thus it is clear that these new indexes could provide useful information to select optimal Arm configurations further.

The values of all the estimative indexes for the selected configurations (for both EFAA-favoured and RA-favoured policies) are shown in Table 5, and Fig. 14.

NO. 2- 29 30 34 35 36 41 59 60
h 2(mm) 156 163 121 128 135 100 156 163
lR (mm) 110 110 130 130 130 150 170 170
NEFAA 29 32 30 30 31 30 50 50
NRA 576 570 571 569 560 562 495 489
Mt (C) 71026 98448 70595 76635 80551 89754 94581 100830
Mt (Cf ) 64.83 92.55 72.99 77.12 78.90 60.51 57.09 59.57
Mt (Cm ) 212.25 311.08 171.75 188.88 201.24 178.42 193.69 208.67
Q 3(C) 83723 185210 183300 201290 183480 148600 105920 112380
Q 3(Cf ) 32.50 163.16 213.12 226.05 186.47






175.16 32.28 33.70
Q 3(Cm ) 309.56 498.23 332.77 371.69 365.79 229.55 338.79 365.39

Table 5.

8 values of the estimative indexes for selected configurations.

Figure 13.

Q 3(C), Q 3(C f ) and Q 3(C m ) of 100 configurations listed in Table 4.

Figure 14.

Plots of values of the estimative indexes of 8 selected configurations.

It is certain that the selected configuration No.2-29, 30, 34, 35, 36, 41 resulted in a larger N RA , and configuration No.2-59, 60 made a larger N EFAA . Considering the N RA , N EFAA and Q 3(C), Q 3(C f ), Q 3(C m ) together, among the RA-favoured configuration, No.2-29, among the EFAA-favoured, No.2-59 are the optimal configurations.

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6. Discussion

Optimal configurations were selected, using the estimative indexes proposed. How the selected configurations meet the requirements of the shoulder prostheses for daily living is the most important concern. Prototyping and experiments in real daily living environment are necessary to give the evaluation. However, on this research stage, preliminary verification could be done by comparing one selected configuration with the initial solution. The comparison was shown in Table 6 and Fig. 15.

Index h 2-l RCombination Upgrading(%)
Initial Optimal(No.2-59)
h 2(mm) 170 156
lR (mm) 250 170
NEFAA 68 50 -26.47
NRA 393 495 25.95
Mt(C) 852240 94581 88.90
Mt(Cf ) 279.41 57.09 79.57
Mt(Cm ) 1195.50 193.69 83.80
Q 3 (C) 160460 105920 33.99
Q 3 (Cf ) 57.51 32.28 43.87
Q 3(Cm ) 324.22 338.79 -4.49

Table 6.

A comparison between the optimal with the initial configuration.

As shown in Table 6, all the other indexes are improved at a price of 26.47% reduce of N EFAA . This could be improved or compensated by 1) including h 1, and disk size r B , r P , as design parameters to enable better combinations; 2) employing a flexible backbone; 3) increasing actuators’ operating range by changing pneumatic actuators, or serially connecting the current actuators.

There is another important clue shown in Fig. 15. There are 2 relative features of the selected configuration: 1) plots of the selected configuration are more compact than the initial solution; 2) the center of the plot distribution locates quite far from the center of the EFAA. Due to the two features, there are fewer points plotted in ΣEFAA. However,if the center of this compact distribution could be directed towards the center of EFAA, much better configuration could be expected. The relocation of the distribution center could be realized by biasing the initial posture of the shoulder prosthesis, i.e., adjusting resting length of actuators.

Considering the fact that the Arm is used as shoulder prostheses, twisting or bending users’ trunk could also contribute to the posture control. However, this is not preferable, since it could result in fatigue damage accumulation in lower back muscles, due to frequent use of upper limb in daily living. That is why the spatial accessibility would be a very important issue in our future research. Moreover, the existence of singular points should be confirmed, and investigation from the viewpoint of mechanics should be done.

Figure 15.

A comparison between the optimal with the initial configuration.

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7. Conclusion

In the research, approach to optimize configuration for shoulder prostheses considering the spatial accessibility and manipulability was proposed. Since for an individual user, the preferable EFAA and RA might be different due to individual difference in daily living style and tasks, and physical constitution, rather than configuration itself, the approach to find the configuration is more important. Thus our research could facilitate the design process of shoulder prostheses with constrained functional elements.

In the near future, estimative indexes to evaluate spatial distribution should be devised, with which the items for further investigation mentioned in the section 6 should be carried out and verified.

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Acknowledgments

This work was supported in part by a Grant-in-Aid for Scientific Research (B), 2011, 23300206, from the Ministry of Education, Culture, Sports, Science and Technology of Japan, and by the Mitsubishi Foundation.

References

  1. 1. Airic’s_arm(2000-2008).March 2.2011 Available from: <http://www.festo.com/cms/en-us_us/5009.htm>,Festo AG & Co. KG
  2. 2. Arai T. 1992Analysis and Synthesis of a Parallel Link ManipulatorBased on Its Statics, Journal of the Robotics Society of Japan,10 4 526 533in Japanese).
  3. 3. Folgheraiter M. Gini G. 2005MaximumOne: An Anthropomorphic Arm with Bio-inspired Control System, Biomimetic Neural Learning for intelligent robots, LNAI 3575, 281 298 978-3-54027-440-7
  4. 4. Jacobson S. C. Knutti D. F. Johnson R. T. Sears H. H. 1982Development of the UtahArtificial Arm, IEEE Transactions on Biomedical Engineering, 29 4 249 269April
  5. 5. Ku D. M. 1999Direct displacement analysis of a Stewart platform mechanism, Mechanism and Machine Theory, 34, 453 465
  6. 6. Merlet J. P. 1993Direct kinematics of parallel manipulators, IEEE Transactions on Robotics and Automation, 9 6 842 846December
  7. 7. Nasu M. Ohnishi K. Tajima T. Saito Y. 2001Study on Hybrid Electric Prosthesis for Single Arm Amputee, Proceedings of the 7th Conference on Japan Society of Mechanical Engineers Kanto Branch, 7 133 134March 9, 2001, Japan (in Japanese)
  8. 8. Press W. H. Teukolsky S. A. Vetterling W. T. Flannery B. P. 1992 Numerical Recipes in C The Art of Scientific Computing Second Edition, 379 383Cambridge University Press
  9. 9. Revolutionizing Prosthetics 2009March 23, 2011, Available from: <http://www.jhuapl.edu/ourwork/stories/st090829.asp>,TheJohns Hopkins University Applied Physics Laboratory
  10. 10. The investigation of disabled person and child. 2005March 23, 2011, Available from: <http://www.mhlw.go.jp/toukei/list/108 1 .html>,Ministry of Health, Labour and Welfare (in Japanese)
  11. 11. Troncossi M. Borghi C. Chiossi M. Davalli A. Parenti-Castelli V. 2009aDevelopment of a prosthesis shoulder mechanism for upper limb amputees: application of an original design methodology to optimize functionality and wearability, Medical and Biological Engineering and Computing, 47 5 523 531
  12. 12. Troncossi M. Gruppioni E. Chiossi M. Cutti A. G. Davalli A. Parenti-Castelli V. 2009bA Novel Electromechanical Shoulder Articulation for Upper-Limb Prostheses: From the Design to the First Clinical Application, JPO Journal of Prosthetics and Orthotics, 21 2 79 90April 2009,
  13. 13. Troncossi M. Parenti-Castelli V. Davalli A. 2005Mechanical design of a prosthetic shoulder mechanism for upper limb amputees, Proceedings of the 2005 IEEE 9th International Conference on Rehabilitation Robotics,June 28July 1, 2005, Chicago, IL, USA
  14. 14. Utah Arm. . March 23, 2011Available from: <http://www.utaharm.com/ua3.php>,Motion Control, Inc.
  15. 15. Yoshikawa T. 1988 Foundations of Robot Control, Corona Publishing Co., Ltd., 978-4-33904-130-9in Japanese)

Written By

Masashi Sekine, Kento Sugimori and Wenwei Yu

Submitted: 17 November 2010 Published: 29 August 2011