Fig. 1. The PerMMA is used to open a closet in kitchen.

Abstract—In this paper, we investigate the enhanced ability ofmanipulation with the newly developed Personal Mobility andManipulation Appliance (PerMMA). PerMMA is a new assistivedevice that integrates bimanual manipulation with smartmobility to assist people with severe physical disabilities andenhance their quality of lives. Different from the fixed mountingmethod used in most existing systems, a novel mounting systemwas designed on PerMMA to enhance its capability ofmanipulation assistance. With a workspace characterized byessential daily living tasks, we evaluated PerMMA’sperformance of manipulation using a comparative studybetween PerMMA and classic design, such as single arm andfixed mounting, used in most existing systems. Simulationresults demonstrate significant improvements with PerMMA inboth of its reachability and manipulability.

I. INTRODUCTION

VER 10 million Americans reported a daily activitylimitation in the 2008 Census, whose activities of daily

living (ADLs) usually require assistance from tools orpersonal caregivers [1][2]. However, the shortage and highcost of experienced caregivers fail to fulfill the rapidlygrowing needs for more personal assistance. Technologywhich aids in these tasks is in great demand, and it must allowthe user to independently and safely control both mobility andmanipulation within an unstructured environment in theirhome and community [3].

Robotics technology has been applied in rehabilitationtechnology and assistive devices to enhance the performanceof assistance and quality of life of people with disabilities. Byattaching a robotic manipulator to a mobile base, such as awheelchair or a mobile robot, several robotic assistive deviceshave been developed to provide both mobility andmanipulation assistance to people with severe physicalimpairments [9-12]. However, most existing devices onlyprovide a single-arm manipulation, which greatly reduce theirefficiency of assistance and restricts their ability to performcomplex manipulation tasks which require the involvementsof both arms, for example, open the refrigerator with one arm

This work was supported by the U.S. National Science Foundation(grant#EEC-540865), the US Department of Veterans Affairs(grant#B3142C and #B6789C) and the National Institute for Disability andRehabilitation Research (grant#H133P09001002). The contents of this paperdo not represent the views of the Department of Veterans Affairs or the

United States Government. .The authors are with the Human Engineering Research Laboratories, the

Department of Rehabilitation Science and Technology, University ofPittsburgh, and the VA Pittsburgh Healthcare System, Pittsburgh, PA, USA(Email: jix33@pitt.edu).

and pick up a bottle of water with the other one.In this paper, we investigate enhanced manipulation

assistance with our newly developed Personal Mobility andManipulation Appliance (PerMMA), as shown in Fig. 1.PerMMA is capable of providing efficient and flexiblebimanual manipulation as well as smart mobility to peoplewith severe physical disabilities. Different from the fixedmounting method used in most existing systems, a novel trackand carriage mounting system is developed, which not onlypreserves relative mobility between the base and the arms, butalso provides extra degrees of freedom (DoFs) to the robotarms. PerMMA’s capability of manipulation was evaluatedusing numerical analysis within a workspace characterized byessential daily living tasks. Two important criteria,reachability and manipulability, are compared betweenPerMMA and classic single arm fixed mounting designs.

II. RELATED WORK

Power wheelchairs are important appliances for mobilityassistance for people with severe physical disabilities. Since apowered wheelchair has similar characteristics as a mobilerobot in mechanical structure, drive-systems and navigationmethods, robotics technology has been applied to poweredwheelchairs to achieve more intelligent mobility assistance.An example of a combination of a mobile robot and poweredwheelchair is the IBOT, which is a wheelchair that can raisethe user up to eye level or climb stairs. Studies have shownthat the IBOT has the potential to improve employment

Enhanced Bimanual Manipulation Assistance with the PersonalMobility and Manipulation Appliance (PerMMA)

Jijie Xu, Member, IEEE, Garrett G. Grindle, Ben Salatin, Juan J. Vazquez, Hongwu Wang, Dan Ding,Member, IEEE, and Rory A. Cooper, Fellow, IEEE

O

The 2010 IEEE/RSJ International Conference on Intelligent Robots and Systems October 18-22, 2010, Taipei, Taiwan

978-1-4244-6676-4/10/$25.00 ©2010 IEEE 5042

Fig. 2. Design of the track and carriage system of the PerMMA.

satisfaction of wheelchair users and increase theirparticipation in community activities [4]. Another roboticwheelchair, the TopChair, has four wheels for driving anduses tracks to climb stairs and shows good performance incurb negotiation and stair climbing [5]. Utilizing differentsensors, several robotic wheelchairs, such as the Wheelsley,RobChair and Rolland, can automatically navigate with adirection commanded by the user while avoiding obstacles[6-7]. However, many smart wheelchair users still havedifficulty in retrieving a remote control, book/magazine, or adrink if not placed in their immediate proximity. Therefore,the capability of providing manipulation assistance togetherwith enhanced mobility is in great need for personal assistivedevices.

Robot arms have advanced in the past two decades to allowpeople with upper extremity impairment or amputation toretrieve partial or full capability of completing manipulationtasks in their daily living [8]. An early manipulationassistance system utilizing robot arms was the DesktopVocational Assistant Robot (DeVAR) [9], which consisted ofa small robotic arm mounted on an overhead track systemabove a desk and was controlled using discrete word voicecommands. Following the DeVAR was the ProfessionalVocational Assistant Robot (ProVAR), which incorporatedforce sensors and different interface modes [10]. With 6degrees of freedom and a universal docking socket at bothends, the ASIBOT allows either end to function as the fixedpoint or the gripper [11]. By mounting a Barrett WAM armand hand on a mobile base, the Home Exploring RoboticButler (HERB) was developed as a platform to validateadvanced machine intelligence algorithms [12].

One of the most commonly investigated robotic arms inrehabilitation research is the commercially available ManusAssistive Robot Manipulator (ARM) [13]. The ARM has 6degrees of freedom (DoFs) plus a simple two-fingeredgripper for general manipulation. An advantage of the ARMis its compatibility to wheelchairs and other mobile bases,which makes it a good tool to provide mobile manipulationassistance [14]. The ARM has also been attached to a smallmobile robot to follow the wheelchair user around andprovide manipulation assistance [15].

Several customized robotic assistive devices combing bothmobile base and robot arm have been developed to overcomethe limitations of the Manus ARM in the range of movementsand dexterity. The KIAST Rehabilitation EngineeringService (KARES) developed at the Korean Institute forAdvanced Science and Technology (KAIST) attach acustomized 6-DOF robotic arm to the side of an EPW [16]. A9 DoFs robotic arm developed by the University of SouthernFlorida tried to provide more DoFs to achieve more dexterityin manipulation assistance [17]. A new robot specificallydesigned for door opening task, the DORA, is beingdeveloped at University of Massachusetts, Lowell [18].However, customized systems are still not available forpractical rehabilitation applications because of availability,safety and reliability concerns. A safe and efficient assistivesystem that can perform real tasks for people with disabilitiesin their home is in great need.

III. DESIGN OF PERMMA AND THE NOVEL MOUNTING

SYSTEM

Most mobility assistive devices lack manipulativecapability to provide users with limited hand dexterity orfunction the ability to perform activities like opening a door,holding a glass of water, or preparing food in a microwave.The ultimate goal of the personal mobility and manipulationappliance (PerMMA) is to provide a “zero-gap” in bothmobility and manipulation between people with disabilitiesand unimpaired person [19]. Therefore, it should provide itsusers with both intelligent mobility and intuitive bimanualmanipulation. Considering the safety and reliabilityrequirement for the entire system in practical daily use, wehave chosen to utilize commercially available products withadd-on customized features to build the PerMMA, althoughseveral fully customized systems have been investigated byother researchers. A commercialized PerMobil C500(PerMobil Inc, USA) electric powered wheelchair (EPW) wasselected as the mobile base because of its flexibility andpowered seating system. The original mechanical structureand user-machine interface of the C500 was adopted to allowusers to control the mobility and seat functions, but alloriginal electronics were replaced with customizedsub-systems for integrating advanced features. Anafter-market encoder was attached to the caster of the C500and a 6-DoF inertia sensor was integrated into the seat todetect vibration, roll rates and wheel slip while PerMMA isdriven over different terrains. A control algorithm based on a3D kinematics model of the C500 was developed toautomatically switch between velocity/traction control modesto reduce the wheel slip and provide robust mobilityassistance on different terrains [20].

To provide people with severe physical impairments withthe enhanced capability of manipulation is another importantconcern in the design of the PerMMA. Many essentialmanipulation tasks in daily living require the involvement ofboth arms, for example, holding a bottle with one hand whileopening the cap with the other one. The capability ofproviding bimanual manipulation will significantly improvethe efficiency and usability of manipulation assistance. As the

5043

first assistive device that provides bimanual manipulation,PerMMA integrates two Manus ARMs with itbase. The two ARMs are symmetric in their mechanicalstructure and provide a much larger reachable range formanipulation. Although several mounting patterns for awheelchair mountable robot arm have been introduced inliterature [21], including front mounting, side mounting andrear mounting, all of these mounting patterns fix the robotarm position with respect to the mobile base. Once an objectis out of the range of the robot arm, the user has to move thewheelchair to re-approach the object in order to perform themanipulation, which greatly restricts the effectivenessefficiency of the robot arm. Different from classicmethods, we developed a novel track and carriagemount two Manus ARMs on the C500 EPW2, which preserves the relative mobility between themanipulator and the mobile base. A U-shapedattached to the seat frame and can move with the powered seatfunction, which provides the users the same capability ofmanipulation no matter which direction they are facing andhow they are seated. A short supporting bridgeto each ARM, and was connected to amounted on the track. The carriage system allows eachto move along the track as well as rotate about the axis of thecarriage, which provides two extra DoFs in addition tooriginal 6 DoFs of the Manus ARM. The entire track is withinthe footprint of the mobile base, which addand does not affect the original seating functions of the C500The extra translational DoF not only allows both Aapproach target objects without base movement, but also canrelocate them behind the seat back along the tracktwo ARMs are folded and hidden behind the seatextra width will be added, which maintains the same mobilityof PerMMA in narrow environments, such as doorways andhallways. The extra rotational DoF allows both ARMs tore-orientate to face all directions on the sidewithout moving the mobile base. This track and carriagesystem significantly enhances the flexibility and easof the system and improves the efficiency of the manipulationand the effectiveness for the users.

IV. KINEMATICS OF PERMMA’S BIMANUAL

The kinematics model of the PerMMA with two ARMsmounted using the track and carriage sabstracted as shown in Fig. 3. Following the notations in [let be the rotational axis of a revolute joint and

point on this axis, then a revolute joint can be represented by

its twist coordinates and

joint , where is the translational velocity generated

by this joint. For a prismatic joint, let represent

of the translation, a prismatic joint can be represented by its

twist coordinates and its translational motion

Let us first consider kinematics of the left ARM. Sinceright ARM is similar to the left one in kinematics and

Fig. 4. Workspace characterized by daily living tasks

Fig. 3. Kinematics model of PerMMA: two ARMs on the wheelchairwith the track and carriage system.

first assistive device that provides bimanual manipulation,PerMMA integrates two Manus ARMs with its smart mobile

The two ARMs are symmetric in their mechanicalstructure and provide a much larger reachable range for

everal mounting patterns for aeen introduced in

front mounting, side mounting and, all of these mounting patterns fix the robot

the mobile base. Once an objectis out of the range of the robot arm, the user has to move the

ect in order to perform theeffectiveness and

Different from classic mountingand carriage system to

mount two Manus ARMs on the C500 EPW, as shown in Fig.the relative mobility between the robot

shaped track wasmove with the powered seat

, which provides the users the same capability ofmatter which direction they are facing and

bridge was attachedcarriage system

The carriage system allows each ARMbout the axis of the

, which provides two extra DoFs in addition to theThe entire track is within

adds no extra widththe original seating functions of the C500.

allows both ARMs towithout base movement, but also can

back along the track. When thehind the seat back, no

maintains the same mobilityof PerMMA in narrow environments, such as doorways and

rotational DoF allows both ARMs toon the side of the PerMMA

without moving the mobile base. This track and carriagethe flexibility and ease of use

the efficiency of the manipulation

IMANUAL MANIPULATION

the PerMMA with two ARMsmounted using the track and carriage system can be

. Following the notations in [22],be the rotational axis of a revolute joint and be a

revolute joint can be represented by

and the value of this

is the translational velocity generated

represent the direction

prismatic joint can be represented by its

its translational motion .

the left ARM. Since thein kinematics and they are

symmetrically mounted on both sides ofkinematic model of the right ARM can be obtainedthe same procedure. Attaching a whe

center of the seat on the EPW and a

gripper of the left ARM. The six revoluteARM can be represented by their twists

and its six joint angles

Similarly, the revolute joint on the track and the prismaticjoint on the carriage can be represented by their twistcoordinates

and the translational motion along the trackrotation angle of the carriage, .

Let represent

transformation of frame relative to frame

Workspace characterized by daily living tasks

: two ARMs on the wheelchairwith the track and carriage system.

mounted on both sides of the mobile base, thekinematic model of the right ARM can be obtained following

a wheelchair frame, , to the

gripper frame, , to the

revolute joints of the leftir twists coordinates

.

Similarly, the revolute joint on the track and the prismaticjoint on the carriage can be represented by their twist

motion along the track, , and the

represent the rigid body

relative to frame , where

5044

(a)

(b)Fig.6. Reachability with track and carriage system: (a) Left ARM;(b) Right ARM.

-1000

-500

0

500

1000 -1000-500

0500

1000

-500

0

500

1000

1500

2000

-1000

-500

0

500

1000 -1000-500

0500

1000

-500

0

500

1000

1500

2000

(a)

(b)Fig. 5. Reachability with side mounting: (a) Left ARM; (b) RightARM.

-1000

-500

0

500

1000 -1000-500

0500

1000

-500

0

500

1000

1500

2000

-1000

-500

0

500

1000 -1000-500

0500

1000

-500

0

500

1000

1500

2000

represents the translation between two frames and

is the rotation matrix. Let represent the

rigid body transformation of frame relative to frame

when the left ARM is in its reference configuration. Theforward kinematics of the left ARM is [22]

. (1)

Let be the spatial velocity of the frame

relative to the wheelchair frame , where is

the translational velocity and is the rotational

velocity. Its relationship with the joint values of the left ARM

can be represented as where is

the spatial Jacobian of the left ARM and

is the ARM’s configuration.

With the similar procedure, we can calculate the rigid bodytransformation of the right ARM and its spatial

Jacobian matrix in terms of the right ARM’s

configuration by following its forward kinematics.Interested readers can refer to [22] for more details on twistcoordinates and the product of exponentials method.

V. ENHANCED MANIPULATION ASSISTANCE WITH PERMMA

For a manipulation assistance device, its ability to reach acertain configuration is one of the important criteria toevaluate its usability and performance. In order to providepeople with disabilities the same capability of manipulationas people with no impairment, the system should be able tocomplete most essential tasks that are tightly related to theindependent living of people with disabilities, which includeretrieving objects from the floor, picking up objects from ahigh shelf, retrieving food from refrigerator, feeding andhygiene, dressing, etc [23, 24]. Parameterized by the width(w), depth (d) and height (h), the desirable workspace formanipulation assistance can be evaluated using these dailyliving tasks, as shown in Fig. 4. Since the PerMMA combinesmobility assistance with manipulation assistance, withoutloss of generality, we define the local workspace as a relativeregion around the mobile base and we only analyzePerMMA’s reachability in this local workspace withoutmovement of the mobile base. The general reachability ofPerMMA can be obtained by expanding this localreachability using movements of the mobile base.

We define the local workspace of PerMMA, denoted by, as a rectangular cube with w=[-1000, 1000], d=[-1000,

1000] and h=[-450, 1550] (unit: mm), which covers allessential daily living tasks discussed above. Since it isextremely difficult to obtain a closed form of PerMMA’slocal reachability, we applied a numerical analysis to study itsreachability at certain positions within . With a grid size

(mm), we discretized the entire into

grids, as shown in Fig. 6. Considering the safety of the userinside the wheelchair, the workspace within a predefined saferegion is defined to be unreachable to avoid collisions

between the ARMs and the mobile base as well as collisionsbetween the ARMs and the user. Therefore, all the nodesinside the safe region are removed from the workspace andnot considered. Outside the safe region, a total of 1280 gridnodes are defined in PerMMA’s local workspace, and for any

5045

Fig. 9. Manipulability measurement of the left Manus ARM

0 20 40 60 80 100 120 140 160 1800

0.5

1

1.5

2

2.5

3x 10

8 Manipulability of the left ARM at reachable configurations

Index of reachable nodes

Manip

ula

bili

tym

easure

ment

side mounting

track&carriage

Fig. 8. Bimanual reachability of the PerMMA with track and carriagesystem.

-1000

-500

0

500

1000 -1000-500

0500

1000

-500

0

500

1000

1500

2000

Fig. 7. Bimanual reachability of the PerMMA with side mounting.

-1000-500

0500

1000 -1000-500

0500

1000

-500

0

500

1000

1500

2000

grid node, joint values of both ARMS to reach this grid pointare computed with a numerical inverse kinematics algorithmuisng the following procedure: (1) Calculate

; (2) If , calculate current Jacobian

matrix ; (3) Move the ARM toward with for ; (4)

repeat step 1. The movement limits of all joints are defined as,

, and values of all other joints are

limited within .

First, we evaluated the enhanced reachability of thePerMMA provided by our track and carriage system. With aclassic side mounting method, the reachable configurations inthe local workspace of either ARM are shown in Fig. 5. Anode that can be reached by an ARM is represented as “*” andan unreachable node is represented as “ ”. Each ARM is able

to reach 161 grid nodes, out of the total 1280 predefinedconfigurations. With our novel track and carriage system, thereachable configurations in the local workspace of each ARMare shown in Fig. 6. Each ARM now is able to reach 243 gridnodes. Therefore, the reachability of the PerMMA isincreased by 50.93% with our track and carriage mountingmethod.

Second, we evaluated the enhance reachability of thePerMMA provided by our novel bimanual design. It isobvious that the PerMMA can reach much moreconfigurations with two ARMs than only using only one. Thebimanual reachabilitiy of the PerMMA with the classic sidemounting method is shown in Fig. 7. The grid nodes that canbe reached by both ARMs is represented as “o”. Totally 281nodes can be reached by either ARM with the bimanual

design, which is a 74.5% increase compared to a single armdesign. The bimanual reachability of PerMMA with the trackand carriage system is shown in Fig. 8. A total of 445 nodescan be reached by either ARM, which is a 58.4% increaseover the bimanual design with fixed mounting, an 83.2%increase over the single arm design with the track andcarriage mounting, and a 176.4% increase over the single armdesign with fixed mounting. Moreover, either with sidemounting method or with our new track and carriage system,41 nodes can be reached by both ARMs with the bimanualdesign, which are mostly located in front of the user in thewheelchair. This significantly increased the flexibility ofPerMMA’s manipulation assistance, and allows the users tocomplete essential tasks that require involvement of botharms. A summary of the comparison is shown in Table 1.

Singlearm withfixedmounting

Singlearm withtrack andcarriage

Bimanualwith fixedmounting

Bimanual withtrack andcarriag

Reached nodes 161 243 281 445

Increase 0% 50.93% 74.5% 176.4%

Increase - 0% 15.6% 83.2%

Increase - - 0% 58.4%

Table 1. Summary of reacability with different designs

Another important factor to evaluate the performance of amanipulation assistive system is its manipulability, whichrepresents the ability to change its position or orientation in adefined configuration. A frequently used manipulabilitymeasurement is the manipulability ellipsoid, which representsthe ability of the robot to transform a unit movement in jointspace to a movement in its workspace [25]. The volume of theellipsoid can be calculated from the Jacobian matrix of therobot as

. (2)

The manipulability of each Manus ARMs at its reachableconfigurations in was calculated using the measurement(2). For the left ARM, manipulability measurements for itsreachable configurations with classic side mounting methodand the proposed track and carriage system are shown in Fig.9. Manipulability measurements of the right ARM is shownin Fig. 10. Comparing with the rigid side mounting method,the track and carriage system obviously improves themanipulability of both Manus ARM at all reachableconfigurations. The minimal increase is 53.57% for both

5046

Fig. 10. Manipulability measurement of the right Manus ARM

0 20 40 60 80 100 120 140 160 1800

0.5

1

1.5

2

2.5

3x 10

8

Index of reachable node

Manip

ula

bili

tym

easure

ment

Manipulability of the right ARM at reachable configurations

side mounting

track&carriage

Arm, and the maximal increase is over 50000 times.

VI. CONCLUSION AND FUTURE WORK

In this paper, we investigated the enhanced manipulationassistance provided by a newly developed personal mobilityand manipulation appliance (PerMMA). This bimanualdesign of PerMMA significantly improved its performanceand efficiency of manipulation assistance. Different from allexisting systems, we developed a novel mounting system toattach two ARMs on a PerMobil C500 EPW, which not onlypreserved the relative mobility between the ARMs and thebase but also provided two extra DoFs to each ARM. With aworkspace characterized by essential daily living tasks, weevaluated PerMMA’s reachability and manipulability with acomparative study between PerMMA and classic design usedby other existing systems. Simulation results have shown thatthe bimanual design and the novel track and carriage systemgreatly improve the reachabilty of the ARM and significantlyincrease the manipulability of the ARM in the workspace.

In this paper, we did not consider the mobility of the basein our analysis. In future work, we plan to investigate thecoordination between mobility and manipulation, and utilizethe mobile base and seating functions to further improve themanipulation assistance. Moreover, we will design dailyliving experiments to evaluate performance of the PerMMAin bimanual manipulation tasks.

REFERENCES

[1] http://www.census.gov/hhes/www/disability/disability.html, accessedOctober, 18, 2008.

[2] http://www.sci-info-pages.com/facts.html, Spinal Cord Injury Factsand Statistics.

[3] Platts RG, Fraser MH. Assistive technology in the rehabilitation ofpatients with high spinal cord lesions. Paraplegia, vol. 31, no. 5, pp.280-287, 1993.

[4] Uustal H, Minkel JL. Study of the independence IBOT 3000 mobilitysystem: An innovative power mobility device, during use in communityenvironments. Archives of physical medicine and rehabilitation, vol.85, no. 12, pp.2002-2010, 2004.

[5] Laffont I, Guillon B, Fermanian C, et al. Evaluation of a stair-climbingpower wheelchair in 25 people with tetraplegia. Archives of physicalmedicine and rehabilitation, vol. 89, no. 10, pp. 1958-1964, 2008.

[6] Yanco HA, Wheelesley: A robotic wheelchair system: Indoornavigation and user interface, Lecture Notes in Computer Science,Springer, Vol. 1458, pps. 256-268, 1998.

[7] G. Pires, U. Nunes, A. T. de Almeida, ROBCHAIR - ASEMI-AUTONOMOUS WHEELCHAIR FOR DISABLEDPEOPLE,

Proc. 3rd IFAC Symposium on Intelligent Autonomous Vehicles, pps.648-652, 1998.

[8] J.L. Pons, R. Ceres and F. Pfeiffer. Multifingered dextrous roboticshand design and control: a review. Robotica, Vol. 17, pp 661-674,1999.

[9] Leifer L, Van dL, Lees D. Visual language programming: For robotcommand/control in unstructured environments. Proceedings of the 5thInternational Conference on Advanced Robotics, vol. 1, pp. 31-36,1991.

[10] Wagner JJ, Van der Loos H. Training strategies for the user interface ofvocational assistive robots. Proceedings of the 26th AnnualInternational Conference of the IEEE Engineering in Medicine andBiology Society, vol. 2, pp. 5423-5425, 2004.

[11] Peña González AI, Gil-Agudo AM, Jardón AH. Functional evaluationof ASIBOT, a portable robot to aid disabled persons. Proceedings of theInternational Congress on Domotics, Robotics and Remote-Assistancefor All, pp. 79-86, 2007.

[12] Diankov R, Srinivasa SS, Ferguson D, Kuffner J. Manipulationplanning with caging grasps. Proceedings of the 8th IEEE-RASInternational Conference on Humanoid Robots, pp. 285-292, 2008.

[13] Allart B, Marhic B, Delahoche L, Remy-Neris O. Navigation paradigmof a prehensive robotics assistance. Proceedings of the IEEE/ASMEInternational Conference on Advanced Intelligent Mechatronics, pp.1-6, 2007.

[14] Rosier JC, Van Woerden JA, Van der Kolk LW, Driessen BJF, KweeHH, Duimel JJ, Smits JJ, Tuinhof de Moed AA, Honderd G, Bruyn PM.Rehabilitation robotics: The MANUS concept. Proceedings of the 5thInternational Conference on Advanced Robotics, vol. 1, pp.893-898,1991.

[15] Cauchois C, de Chaumont F, Marhic B, Delahoche L, Delafosse M.Robotic assistance: An automatic wheelchair tracking and followingfunctionality by omnidirectional vision. Proceedings of the IEEE/RSJInternational Conference on Intelligent Robots and Systems, pp.2560-2565, 2005.

[16] Bien Z, Kim D, Chung M, Kwon D, Chang. Development of awheelchair-based rehabilitation robotic system (KARES II) withvarious human-robot interaction interfaces for the disabled.Proceedings of the IEEE/ASME International Conference on AdvancedIntelligent Mechatronics, vol. 2, pp. 902-907, 2003.

[17] Yu W, Alqasemi R, Dubey R, Pernalete N. Telemanipulation assistancebased on motion intention recognition. Proceedings of the IEEEInternational Conference on Robotics and Automation, pp. 1121-1126,2005.

[18] Katherine M. Tsui, Holly Yanco, David Kontak, and Linda Beliveau.Development and Evaluation of a Flexible Interface for a WheelchairMounted Robotic Arm. Proceedings of the ACM SIGCHI/SIGARTHuman-Robot Interaction Conference, March 2008.

[19] Cooper RA, Wheeled Mobility and Manipulation Technologies, TheBridge, vol. 39, no. 1, pp. 13-20, 2009.

[20] Wang H, Salatin B, Grindle GG, Ding D, Cooper RA. “Real-TimeModel-Based Electric Powered Wheelchair Control”. MedicalEngineering and Physics, in press, 2009.

[21] Warner PR and Prior SD, “Investigations into the Design of aWheelchair-mounted Rehabilitation Robotic Manipulator”,Proceedings of the 3rd Cambridge Workshop on RehabilitationRobotics, Cambridge University, England, April 8, 1994.

[22] Murray R, Li Z and Sastry SS, “A Mathematical Introduction toRobotic Manipulation”, RCR Press, 1994.

[23] Prior SD. An electric wheelchair mounted robotic arm--a survey ofpotential users. Journal of Medical Engineering & Technology, vol. 14,

no. 4, pp. 143-154, 1990.[24] Hillman M, Hagan K, Hagan S, Jepson J and Orppwood R, “A

wheelchair mounted assistive robot”, Proceedings on IEEEInternational Conference on Rehabilitation Robots (ICORR), 1999.

[25] Yoshikawa T, “Foundations of robotics: analysis and control”, the MITpress, 1990.

5047