IROS2019国际学术会议论文集Voice-Controlled Flexible Exotendon FLEXotendon Glove For Hand Rehabilitation

1、Voice-Controlled Flexible Exotendon (FLEXotendon) Glove For Hand Rehabilitation Phillip Tran*, Seokhwan Jeong and Jaydev P. Desai, Fellow IEEE AbstractIn this work, we propose a voice-controlled hand rehabilitation device driven by exotendons. A smartphone- based voice recognition system interprets

2、user intention and is utilized for various grasping tasks. A bio-inspired tendon routing mechanism provides four-degrees-of-freedom (DoFs) across the thumb, index fi nger, and middle fi nger. A novel thumb sleeve design is presented for stable thumb movement. The exoskeleton is fabricated from polyu

3、rethane rubber and rigid 3D-printed parts to provide form-fi tting properties while constraining tendon motion. Twisted string actuators and spring units provide active fl exion and passive extension, respectively. The compact nature of the actuation unit allows for placement on the forearm, improvi

4、ng the portability of the system. The voice control system allows for easy user manipulation and accessibility and may improve rehabilitation effi ciency. The performance of the tendon routing and thumb sleeve design were experimentally evaluated and voice control system was evaluated with various g

5、rasping tests. I. INTRODUCTION Affl ictions that impair the upper extremity (arms, hands, and fi ngers), such as spinal cord injury (SCI) or stroke, have been shown to have detrimental effects on quality of life and patient independence 1. For example, a C-5 SCI denervates the hand and fi ngers, ren

6、dering the patient incapable of performing most activities of daily living (ADL) without assistance 2. The upper extremity (UE) is important for many ADL tasks and rehabilitation of the hand and fi ngers can potentially restore functionality 3. The repetitive task practice (RTP) therapy protocol has

7、 been used successfully as a strategy for UE rehabilitation 4. In RTP, the patient repeatedly performs intensive mo- tions associated with certain tasks, such as grasping, in an effort to induce neuroplastic changes for restoration of UE motor functionality 5. However, RTP rehabilitation requires se

8、veral hours of physical therapy per week and a physical therapist must manually assist the patient with each movement 4. Robotic rehabilitation exoskeletons are a feasible alternative because they do not fatigue and can automate some aspects of physical therapy, reducing the burden placed on the the

9、rapist. Numerous robotic hand rehabilitation exoskeletons have been developed for the purpose of assisting patients during hand rehabilitation therapy. The HANDEXOS and HX ex- oskeletons are examples of conventional hand exoskeletons This work was supported in part by the Craig H. Neilsen Foundation

10、. P. Tran, S. Jeong, and J. P. Desai are with the Medical Robotics and Automation (RoboMed) Laboratory, Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA, USA. *P. Tran is the corresponding author . that use rigid components and st

11、andard actuation mecha- nisms (gears, pulleys, linkages, etc) placed on the fi ngers to assist with hand movement 6, 7. Other hand rehabilitation exoskeletons that also actuate multiple DoFs have been developed with similar designs 8, 9. However, conventional hand exoskeletons are often large and ob

12、trusive, restricting the users freedom of movement. Soft exoskeletons have been developed to reduce the com- plexity, size, and weight of rehabilitation exoskeletons 10 12. In particular, tendon-actuated soft exoskeletons (exoten- don systems) have become a viable alternative. The exoten- don system

13、s follow a bio-inspired approach for fi nger actua- tion by partially replicating the natural mechanism of motion in human fi ngers. By routing artifi cial tendons through spe- cifi c positions along the fi nger, exotendon systems can induce fi nger movement, such as extension or fl exion, through t

14、he movement of those tendons. This eliminates the need for complicated mechanisms, reducing the weight and number of components required for exoskeleton function. A disadvantage of exotendon systems is the inherent insta- bility of the exoskeleton itself; because the exoskeleton is de- formable, the

15、 tendons are not constrained and this results in inconsistent fi nger movement and force generation. Recently, silicone-based exotendon systems have been developed to overcome this obstacle because silicone is suffi ciently strong to maintain tendon position for improved performance and yet deformab

16、le enough to tightly fi t around the users hand 5, 13. Though this presents a signifi cant advancement in exotendon systems, the obstacle of limited motion remains. Most hand rehabilitation exoskeletons are not truly portable because of immobile control stations, actuator blocks, or both. This gener

17、ally means that the user is restricted to a small region of movement because the UE cannot move beyond a certain range away from the stationary compo- nents of the exoskeleton. Additionally, hand exoskeletons often rely on manual control, meaning that commands for numerous postures are manually ente

18、red into a program on a computer for exoskeleton operation. This reduces the effi ciency of rehabilitation because the patient cannot control the exoskeleton themselves due to their impairment, and there is delay between patient command and exoskeleton actuation due to human interaction. Moreover, p

19、atients may have diffi culty giving the exact command to achieve various task-specifi c grasping. The exoskeleton presented in this paper, called FLEXoten- don glove, is a voice-controlled hand rehabilitation system that incorporates exotendon routing and a soft exoskeleton. The soft exoskeleton con

20、sists of rigid and soft components 2019 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS) Macau, China, November 4-8, 2019 978-1-7281-4003-2/19/$31.00 2019 IEEE4834 RTR modules RHP blocks Elastic bands Teflon tubes Spring units Actuation units Separators CMC sleeve Tendons P

21、halange rings Fig. 1: Front and back views of the FLEXotendon glove system. for robustness and fl exibility. A novel tendon-routing mech- anism for the thumb is proposed for stable thumb movement and twisted string actuation (TSA) units are mounted on the forearm for system compactness. Finally, a s

22、martphone voice control system interprets user intention and conveys the command to the actuation controller, which may increase effi ciency of the rehabilitation process. This paper is organized as follows. Section II describes the design, actuation mechanism, and voice control system of the FLEXot

23、endon glove. Section III discusses the experimental methods used for evaluation of the FLEXotendon glove as well as the experimental results. Finally, the discussion and conclusions are presented in Sections IV and V, respectively. II. FLEXOTENDONGLOVEDESIGN The FLEXotendon glove is a three fi nger,

24、 four-DoF exo- tendon system that consists of three main components: a hand exoskeleton, an actuation unit, and a smartphone. The hand exoskeleton and actuation unit are shown in Fig. 1. A bio- inspired tendon routing system is implemented to guide the exotendon actuation mechanism used for fi nger

25、movement. The exotendons are connected to the actuation unit, which is composed of four TSA actuation units and four springs. The TSA actuation units control fi nger fl exion and the springs provide passive fi nger extension. The FLEXotendon glove provides independent actuation of the index fi nger,

26、 middle fi nger, and thumb because most ADL tasks can be accomplished using these three fi ngers 5, 14. Detailed designs are presented in the following sections. A. Exotendon Routing The FLEXotendon glove follows a partial biomimetic strategy to achieve fi nger actuation. Fingers in the human hand a

27、re primarily controlled by tendons; specifi cally, fi nger extension and fl exion are controlled by extrinsic tendons located in the forearm 15. Replication of these tendons results in a simple and effective mechanism for controlling fi nger motion, and tendon routing based on the anatomical tendon

28、structure was implemented in the FLEXotendon glove (Fig 2). The exotendons used in the FLEXotendon glove are organized in parallel pairs to prevent force imbalance during Exotendon Elastic phalange rings Teflon tube Index/middle finger flexor tendon Thumb flexor tendon Thumb adductor tendon Index/mi

29、ddle finger extensor tendon Thumb extensor tendon Thumb abductor tendon a)b) Fig. 2: Tendon routing of the FLEXotendon glove: a) Front view and b) Back view actuation. Force imbalance can cause unintended movement along the adduction/abduction DoF in the fi nger, which can shift the fi nger from the

30、 desired trajectory. In the index fi nger and middle fi nger, the fl exor exotendon pair (red line in Fig. 2) and the extensor exotendon pair (blue line in Fig. 2) mimic the function and routing path of the fl exor digitorum profundus (FDP) tendon and the extensor digitorum communis (EDC) tendon in

31、the hand, respectively. Both sets of exotendons pass across the metacarpopha- langeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints and terminate at the fi ngertip. Shortening of each tendon pair generates independent fl exion and extension of the index and middle fi

32、 nger, respectively, and they are actuated with an underactuated mechanism. Due to the complicated confi guration of the thumb, it has been diffi cult to implement multi-DoF thumb movement in hand exoskeleton devices. The carpometacarpal (CMC) joint of the thumb can perform complex movements because

33、 it is controlled by various tendons and intrinsic hand muscles. The abductor pollicis longus (APL) tendon, adductor pollicis muscle (APM), and opponens pollicis muscle (OPM) are the major contributors for adduction/abduction movement of the thumb 16. Additionally, the fl exor pollicis longus (FPL)

34、and extensor pollicis longus (EPL) tendons induce fl exion and extension of the thumb, respectively. Therefore, the major movements of the thumb can be replicated by four sets of exotendons as shown in Fig. 2. The adductor (yellow line in Fig. 2) and abductor (black line in Fig. 2) exotendons contro

35、l the adduction and abduc- tion of the CMC joint at the base of the thumb, respectively. The thumb fl exor exotendon pair (green line in Fig. 2) and the thumb extensor exotendon pair (purple line in Fig. 2) replicate the FPL and EPL in the thumb, respectively. These use the same underactuation mecha

36、nism as the fl exor and extensor exotendons in the index fi nger and middle fi nger. However, the complicated shape of the thenar eminence makes it diffi cult for soft exoskeletons to maintain a stable CMC position. To implement multi-DoF thumb movement with improved stability, the adductor and abdu

37、ctor exoten- dons are wrapped around the thenar eminence of the thumb 4835 Elastic phalange rings Rigid tendon routing (RTR) module Twisting separator modules Elastic CMC sleeve RTR modules Rigid hyperextension prevention(RHP) blocks Elastic phalange rings Elastic band a) b) Elastic bands Twisted pa

38、rt Linear part c) Teflon tubes Fig. 3: Design of the soft exoskeleton. a) Overview of the FLEXotendon glove exoskeleton. b) Tendon routing structure for fl exion and extension. c) Passive hyperextension prevention module. on the front and back sides of the hand, respectively (Fig. 2 (inset). When th

39、e tension increases, the wrapped tendon self-tightens and increases the normal force between the hand and the tendon; this results in an increase of contact force and provides a stable fi t. B. Exoskeleton Design The soft exoskeleton is composed of several components: elastic phalange rings, rigid t

40、endon routing (RTR) modules, twisting separator modules, an elastic CMC sleeve, and elas- tic bands (Fig. 3(a). All elastic components were fabricated using polyurethane rubber (Reofl ex 60, Smooth-On) and all rigid components were manufactured using an ABS-like 3D-printed plastic (VisiJet CR-BK, 3D

41、 Systems). Braided Spectra fi bers (Hercules PE Braided, Hercules Pro) capable of withstanding 23 kere used for the exotendons and measured 0.37 mm in diameter. The elastic phalange rings are custom-molded to fi t each phalange of the fi ngers and small RTR modules are attached to the top and bottom

42、 of each of the rings. The elastic nature of the phalange rings serves as a self-tightening mechanism, reducing displacement due to the tension of the exotendons. The RTR modules incorporate the routing system described in the previous section, constrain exotendon motion, and incorporate Tefl on tub

43、es to reduce friction (Fig. 3(b). Lastly, an elastic band placed around the wrist contains twisting separator modules. The elastic bands are adjustable for a custom-fi t. A pair of exotendons pass through a twisting separator module and RTR module on the palm via Tefl on tubes. The Tefl on tube tran

44、sfers linear motion of the tendon, preventing an extra moment on the wrist. The tendons are connected to the RTR module on the fi nger tip, passing through RTR modules on the proximal and intermediate phalanges to provide fl exion. To provide stable support for the thumb, an elastic CMC sleeve is mo

45、lded from the thenar eminence of a human hand model, and a tendon wrapping mechanism is implemented on the sleeve to provide adduction/abduction. To decouple the fl exion/extension and adduction/abduction, the Tefl on tubes for the thumb fl exor/extensor exotendons are attached to the CMC sleeve (Fi

46、g. 3(a). This confi gura- tion eliminates the infl uence of thumb fl exion/extension on CMC adduction/abduction and vice versa by allowing for independent movement of the thumb joints. To prevent hyperextension, mechanical stoppers are em- bedded for user safety (Fig. 3(c). The extensor exotendons p

47、ass through rigid hyperextension prevention (RHP) blocks placed in between each RTR module. When the extensor exotendons are contracted past a certain distance, the RHP blocks act as mechanical stoppers and passively prevent hy- perextension for user safety. The limit of the extension angle can be i

48、ndividually customized by changing the number of RHP blocks. Additionally, it removes the compression force caused by the passive spring in rest posture. C. Exoskeleton Actuation Design To implement the linear tendon actuation of the FLEXo- tendon glove, we employed the TSA mechanism 1719. TSA is a

49、rotary-to-linear transmission mechanism that can provide a large contractile force with a simple mechanical confi guration. It consists of only a single rotary motor and a pair of tendons as shown in Figs. 4(a). When the motor rotates, the tendons are twisted around each other, which generates a hig

50、h rotary-to-linear trans- mission gain, with more than 90 % transmission effi ciency 18. Due to the nature of light strings and high transmission gain of TSA, the actuation unit can provide large tension to the exotendon without a bulky gearbox. Furthermore, the actuated direction of TSA is parallel

51、 to the axis of the motor; this allows the motors to be placed length-wise on the forearm. This feature provides a space-effi cient arrangement for the actuation unit compared to a pulley-motor based transmission system which requires a set of bevel gears to change the actuation direction. In the im

52、plemented TSA unit (see 4 (b), one end of the tendons is connected to the motor and they pass through a separator module, therefore, the string are twisted only in the section between the motor and the separator and generate linear motion after the separator. The other end of the tendons is connecte

53、d to the RTR module on the fi ngertip. Therefore, the linear displacement of the tendon, which results in fl exion of the fi nger (Fig. 4(b). To estimate displacement corresponding to the rotation of the actuator, a neural network-based fi tting model was employed 20. Because the TSA can only genera

54、te contractile force, spring units are installed on the opposite side of the actuation unit to provide passive fi nger extension (Fig. 1). For user protection, 4836 Bearing connector Rotary motor Tendons Actuator cover Actuation units Separator modules a)b)c) Linear partTwisting part Fig. 4: TSA mec

55、hanism. a) Exploded view. b) Schematic of the TSA mechanism. c) Actuation units. Hand exoskeleton Smartphone Actuation units Fig. 5: Components of the FLEXotendon voice control system. an emergency stop button cuts power to all motors when pressed; the button can be activated at any time and stops a

56、ll actuation in the FLEXotendon glove. D. Voice Control Design A smartphone-based voice recognition system was em- ployed for simple and intuitive grasping control of the FLEX- otendon glove as shown in Fig. 5. The voice recognition- based control can interpret user intention more accurately than ot

57、her methods of control such as electromyography (EMG) or brain control interface (BCI), allowing for a user-friendly control protocol 21. Each voice command is allocated to a specifi c task and thus, there is no uncer- tainty as to the desired motion. Furthermore, the user may have diffi culty contr

58、olling the grasping posture or multiple joint angles for the specifi c tasks through manual control. From an accessibility point of view, voice control is less intimidating to use because it does not require biometric sensor attachment to the user or a complex control inter- face. Additionally, the

59、FLEXotendon glove voice control uses signifi cantly less hardware than EMG, BCI, or manual control, increasing system portability and ease of use. The voice control hardware is comprised of a smartphone and a microcontroller (SAM3X8E, Microchip Technology Inc.) with Bluetooth Low Energy (BLE) capability. The smartphone runs an iOS application that takes user voice commands as input, parses the command for task- Voice Command Natural Language Processing Key Words TaskActuation “Grab the ball” Ball Bottle Cup Grab Hand Open Pen Pinch Grab the ball grab, ball 1 2 3 4 Fig. 6: Schematic