康复机器人的设计-锻炼手臂、手指、下肢等功能（含三维UG图）【11张CAD图纸+PDF图】
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Design and Development of a Portable Exoskeleton Based CPM Machine for Rehabilitation of Hand Injuries* Yili Fu, Peng Wang, Shuguo Wang, Hongshan Liu and Fuxiang Zhang Robotics Institute Harbin Institute of Technology Harbin, Heilongjiang Province, China wangpeng.hit * This work is supported by the National Natural Science Foundation of China (Grant No.60275033) and Key technologies research & development project of Heilongjiang Province in China (Grant No.2006G0845-00). Abstract - Human hand is easy to be injured. As physical rehabilitation therapy after a hand operation always takes a long time, the curative effect gets worse and the social and financial hardship with physical deterioration can be caused. A CPM machine is a mechanism based on the rehabilitation theory of continuous passive motion (CPM). To improve rehabilitation results and validate the CPM theory we have developed a portable exoskeleton based CPM machine. The device can be easily attached and also be adjusted to fit different hand sizes. And during the finger s flexion and extension motion the machine can always exert perpendicular forces on the finger phalanges. It can achieve the precise control of scope, force and speed of the moving fingers. Finally based on its mechanical structure, a kinematic validation and simulation including kinematic simulation and dynamic simulation have been carried out. Index Terms - CPM machine, Exoskeleton, Kinematic validation I. INTRODUCTION The incidence of hand injuries has risen dramatically in the recent years. More than 20 percent and about 40 percent of the cases in the emergency treatment of surgery and orthopaedics are hand trauma. Most of these cases result in loss some of sensation or motion to the arms and hands. Hand therapy is one of great importance because of little muscles all over the hands. So the rehabilitation of the injured hands is a tough task, and the rehabilitation session is long and the recovery of the hand function is not effectively. The impairment of the hand can be the cause of social and financial hardship and a serious cause of physical and emotional deterioration. Now there are mainly three categories of methods for the treatment of hand motion dysfunction during the rehabilitation session. One is physiotherapy, the second is driving movement or passive movement through using the elastic brace. The third takes the method of restoring the injured nerves, relieving the pressures, transplanting and transferring the wholesome muscles and tendons. In recent years, with the development of Continuous Passive Motion (CPM) 1, CPM machines based on this rehabilitation theory have been used widely in the clinical practice. There are various types CPM machines in the market, not only aimed at the function training of big joints such as wrists, elbow joints and hocks, but also used for the rehabilitation of little joints such as knuckles. However, most of these machines are limited in the number of independently actuated degrees of freedom and don t integrate sensors. They cannot do the function training such as adduction and abduction exercise and some dexterous motions such as grasping and holding. Also the rehabilitation therapy of the CPM machines is rest on the level of empiricism. No exact and scientific data can prove their curative effect. So for the reasons above, a new CPM machine is urgent needed to be developed, not only offers a means of hand function rehabilitation, but also offers a means of quantitative detection and evaluation of hand function rehabilitation. So far, most of the hand exoskeletons have been developed for the use as haptic interfaces in master-slave systems. CyberGrasp is one of the commercially available master hands, which can exert feedback forces during flexion at five fingertips 2. It consists of an exoskeleton and uses cables with brakes on their distant end for force transmission. The exoskeleton developed by scientists of the University of Tokyo can covers wide workspace of an operator s finger 3. The exoskeleton has an encounter-type force feedback feature which enables unconstrained motion of the operator s finger and natural contact sensation. There is a question that the force exerted at the finger phalanges by the hand exoskeleton developed for virtual reality often exert in one direction, but for rehabilitation therapy a bidirectional motion is needed. And sometimes the force is too small to move the finger joints for rehabilitation therapy. Exoskeleton based CPM machine such as arm exoskeleton and leg exoskeleton have much been used for the rehabilitation of human big joints. But because of the subtle anatomic structure and so many little joints of the hand, the research on hand exoskeletons becomes very difficult. The hand exoskeleton generally consists of rigid molded plastic as a basic support and hard metal link mechanism as the manipulation method. Rutgers Master ? is an exoskeleton actuated by pneumatic piston which can exert feedback forces against flexion at four fingertips 4. It was employed in a study for the rehabilitation of stroke patients. Another exoskeleton 978-1-4244-1758-2/08/$25.00 2008 IEEE.1476Proceedings of the 2007 IEEEInternational Conference on Robotics and BiomimeticsDecember 15 -18, 2007, Sanya, Chinaactuated by pneumatic piston which can provide assistive force to the user s fingers was developed by scientists of the Carnegie Mellon University 5. The device can provide a coupled active degree of freedom for the DIP and PIP flexion/extension and an active degree of freedom for the MCP flexion/extension for the index finger. Recently a new hand exoskeleton consisted of pulleys and a link mechanism is presented 6. The exoskeleton can support of four degrees of freedom for each finger and fulfil bidirectional movement. Hall sensors are attached on each lever to measure the angle of the finger joints. The University of Salford has developed an exoskeleton based system for the physical and occupational therapy of the hand in an interactive VR environment 7. It give the introduction of accurate and repeatable finger motion and force measurement, interactivity, potential for great exercise assortment and statistical registration and evaluation. All the exoskeleton based CPM machine introduced above cannot exert forces, perpendicular on the finger phalanges, during the complete flexion and extension motion. So the forces pulling or pushing the human joints in a wrong direction would make the injured joints condition worse. The device presented in 8 is similar to the hand exoskeleton presented in this paper. As the authors know, it s application is haptic interaction with a virtual reality, but not for rehabilitation purposes. This paper is organized as follows: Section II proposed the design goals and requirements of the CPM machine. Section III describes the mechanical construction of the device. The kinematic validation of the CPM machine is discussed in section ?. Finally the conclusion of the current work and the possible future improvements are described in the last section. II. DESIGN GOALS AND REQUIREMENTS We set our goals and requirements for designing the CPM machine as follows: ? fit variation of hand sizes ? exerts perpendicular forces on finger phalanges during the complete flexion and extension motion ? bidirectional movement ? mount on dorsal side of the hand and free the palms space Furthermore the device should be light weight, low friction forces high backdrivability during free motion and easy to control. III. MECHANICAL DESIGN A. Function Structure Human hand has a complex structure. There are three joints and four degrees of freedom for per finger and two joints, four degrees of freedom for the thumb. From the distal end for fingers, there are one DOF per DIP (distal interphalangeal) and per PIP (proximal interphalangeal), and two DOF per MCP (metacarpo-phalangeal). For the thumb, there are three DOF for the MCP and one DOF for the IP (interpahlangeal). The flexion/extension of the DIP and PIP joints are coupled, but the DIP/PIP and MCP flexion/extension are independent. Fig.1 shows a human hand physiology. Experiments are carried out to determine the functional modules of human index fingers. Therefore, the length of each knuckle, the moving scope of each knuckle and the driving force for movement of each knuckle of sixty persons at different age groups are measured. The values of the measurement are listed in Table I and Table II. B. Conceptual Design The flexion/extension driving mode consists of three parts: an actuator module, two flexible cables and an exoskeleton, see Fig.2. The actuator module consists of a brushed DC-motor that pulls the flexible cables through a pair of bevel gear. Two flexible spring tubes guide the flexible cables to the exoskeleton. A bidirectional movement is created by looping the cables around a small pulley which has common axis with the spur gear of the exoskeleton. Under the force PIPPIP PIP PIP DIP DIPDIPDIPIPMCPMP1MP1MP 1MP 1MP2MP2MP2MP 2 Fig. 1 Human hand physiology TABLE ? MEASURED LENGTHS OF THE INDEX FINGER KNUCKLES Phalanx Max mm Min mm Average mm DIP 29.0 18.0 24.9 PIP 38.0 29.0 32.8 MP 62.0 43.0 53.0 TABLE ? FLEXION/EXTENSION FUNCTIONAL MODULES OF HUMAN INDEX FINGERS Joints Moving scope Driving force N Max 87.6? 16.1 DIP Min 50.1? 7.0 Max 117.7? 20.0 PIP Min 85.2? 9.0 Max 95.0? 35.0 MP Min 69.5? 11.0 Brushed DC-motorBevel gearFlexible cable MP 1 PIPCircular rackSpur gearHall sensor Fig 2 Driving mode of flexion joint Brushed DC-motorBevel gear Rack Spur gear Fig.3 Driving mode of MP2 joint 1477transferred from the spur gear, the circular rack drives the finger phalange to rotate about the finger joint. The joint angle is measured at the spur gear. The abduction/adduction driving mode also consists of a DC-motor that drives a spur gear though a pair of bevel gears and a rack, see Fig.3. The spur gear is fixed directly on the finger s MP2 joint, which results a rotation of finger phalange. C. Embodiment Design Fig.4 shows a CAD drawing of the exoskeleton for one finger. It is connected to the actuator unit and each phalanx of the finger attachment. To adjust for variations in phalanx length, the circular rack can slide in the guide slot of the force sensor. Exertion of force is possible in both directions. Each circular rack goes into mesh with a spur gear. Each phalanx uses the preceding phalanx as base point for its motion. The circular racks are designed to allow nearly full flexion and extension in all joints. Perpendicular forces are easily realized for all joint angles. They were also designed to be crossed so that the neighbouring circular racks for different phalanxes do not interfere. All joints of the mechanical construction are supported by ball bearings. Fig.5 shows a CAD drawing of the CPM machine s actuator module. In order to simplify the actuator unit, the actions of the DIP?PIP and MCP joints of per finger are coupled together. Abduction and adduction in MCP joint are supported independently. In order to make the mechanism lighter and smaller, driving motors must be placed far from the joints. Therefore, we used wire-driver method. Since one wire can only produce a force in one direction, we use two wires for one joint to produce a bidirectional force. So for one finger six wires are needed. One ends of the six wires are attached to the small pulleys which are placed on the force sensors, and the other ends are attached to another small pulley which is moved by one DC motor with a pair of bevel gears (with 2:1 transmission rate). Considering of the performance, the weight and the noise, finally we choose Portescaps 17N78-216E as the actuating motor. The weight of the motor is 17 g, and the rated power of the motor is 3.2W. The planetary gearhead is built in motor with 88:1 transmission rate. The maximum rotation speed of the finger s MP joint actuated by the CPM machine is 17.7 rpm. The time of the finger s one period motion is 1.48s. The output torque of the actuator unit can reach up to 1 Nm which is enough to actuate the finger. Fig.6 (a) and (b) show the side view of finger with CPM machine in stretched and bent position. Fig.7 (a) and (b) show the top view of finger with CPM machine in normal and abduction position. Close-up view of finger with exoskeleton and actuator module of the CPM machine is shown separately in Fig.8 (a) and (b). D. Sensors of the System A CPM machine needs many force and position sensors to be controlled accurately. The distributing of the sensors can be seen in Table ?. Fig. 4 Exoskeleton of the CPM machine: (a) exoskeleton with stretched finger model, (b) exoskeleton with bent finger, (c) flexion/extension unit of the exoskeleton, (d) exploded view of the flexion/extension unit. Fig. 5 Actuator module of the CPM machine: (a) actuator module, (b) and (c) flexion/extension unit (A) and abduction/adduction unit (B) of the actuator module and an exploded view. Circular rack (a)(b) (d) (c) (a)(b) (c) MPPIP DIPSmall pulleySpur gear2 flexible cables Hall sensor Gear axis2 bearingsMP module PIP module DIP module Force sensor Bearing bracket1 Brushed DC-motor (5)RackSpur gears (4)Bevel gears of A Bevel gears of B Motor of AMotor of BBearing bracket2Small pulley (5)Spur gearGear axis, bearingGuide slot 1478 Fig.6 Side view of finger with CPM machine: (a) in stretched position, (b) in bent position. Fig.7 Top view of finger with CPM machine: (a) in normal position, (b) in abduction position. Fig.8 Close-up view of finger with CPM machine: (a) exoskeleton of the CPM machine, (b) actuator module of the CPM machine TABLE ? THE DISTRIBUTING OF THE SENSORS Sensor type Numbers of sensors per finger Joint position sensor 4 Joint force sensor 3 Motor position sensor 1 The force sensors we used are the traditional strain gage. The mechanical elastic structure of the force sensor, as a mechanical component, mounted inside the flexion/extension module which is shown in Fig.4. The hall joint position sensor fits in the joints of the CPM machine. We use the two-axis Sentron hall sensor 2SA-10 as the sensing element of the position sensors. The motor position sensor is a MR-encoder mounted to the motor shafts which can produce feedback information about the rotation speed of the motor. It can be used in position control loop of the motor. E. Structure Types Analysis We will analyze the structure types from the point of view of the theory of mechanisms. 1) Driving Structure of One DOF Driving structure of one DOF is fixed at DIP and PIP. We suppose that the finger attachments and the phalanges are linked with no relative sliding. Fig.9 (a) shows the schematic diagram of the driving structure of one DOF. The kinematic link has a certain movement. If the small gear rotates with a constant speed, the moment at 2O comes into balance. The 1O2O1222r1r1rFtFnF1TF1l2l Fig. 9 Schematic diagram of two structure types in exoskeleton: (a) driving structure of one DOF, (b) driving structure of two DOF peripheral force tF ?the circumferential force F and the rotation angle 2 of the joint are gotten as follows: 12121222tttTTFFFdd= (1) 6112111219.1 10tTPFFdn d= (2) 1 122rr= (3) Where 1T?2T are torque of the gears, 1d?2d are reference diameter of the gears, P is transmission power, 1n is rotate speed of the small gear, 1r?2r are reference radius of the gears. 2) Driving Structure of Two DOF Fig.9 (b) shows the schematic diagram of the driving structure of two DOF. The relationships of the rehabilitation angle and the rotation angle of AF and the rotation angle of the joint is: 12sinarcsincosll?=+? (4) For MP joint there is 0=, so the rehabilitation angle is gotten as below: 12sinarcsinll?=+? (5) ?. KINEMATIC VALIDATION In order to demonstrate the CPM machine suitability to develop the task it has been designed for, a kinematic validation has been performed. This validation consists of calculation of Forward Kinematics and inverse kinematics. Finally, simulation based on kinematics and dynamics are carried out. The reference coordinates of robot joint is shown in Fig.10. A?Forward Kinematics For the CPM machine, the D-H parameters provide additional information about the types and the sequences of joints in the robot. Kinematics parameters of the robot are shown as Table ?. The position coordinates of the robot s tip is gotten as bellow: (a) (b) (a) (b) (b) (a) (a)(b) 14791Z0Z1Y0X0Y1X1Y2Y3Y1X2X3X01231l2l3l1Z2Z3Z Fig.10 Reference coordinates frames of robot joint TABLE ? KINEMATICS PARAMETERS OF ROBOT Joint i i 1i ia id Range of joint 0 0 0? 0 0 20? 20? 1 1 90? 0 0 0? 90? 2 2 0? 1l 0 0?110? 3 3 0? 2l 0 0? 70? Notation: ia,id represent the length of link i, i,1i represents the angle between joint i and joint 1i 0 1230 12302 0 121 0 10 1230 12302 0 121 0 101012301231231232 121 100001c cc ssl cclc cs cs scl s cls cTA A A Ascl sls+?+?=? Notation:()123123sins=+,()123123cosc=+,()1212sins=+,()1212cosc=+,11sins=,11cosc=,00sins=,00cosc=. B?Inverse Kinematics It is important to calculate the inverse kinematics of the robot for analysis of workspace and control of the robot. Analytic solution and numeric solution are main methods to calculate the inverse kinematics of the robot. The homogeneous transform matrix is shown as below: 030001xxxxyyyyzzzznoapnoapTnoap?=? through the Analytic solution, 0,1,2,3 are gotten as follows: 0arcsinxa= (6) 12arctan= (7) 2arccos2arctan=3arcsinarccos2arctanxn= (8) (9) 1 020xCpBl cCl c = (10) 222AABCBC+? = (11) 2102zAl p s= (12) 102yBl p s= (13) 22222220010zCl sp sl s= (14) C?Simulation Results The simulation consists of two parts: kinematic simulation and dynamic simulation. It should be noticed that there are two basic functions must be provided by the CPM machine: during the safety range it can offer sufficient driving force to make the finger phalanges fulfill bidirectional movement and can make the injured finger do exercise within the maximum angle range to get the best curative effect. Thus, typical functions of robot mentioned above are validated by means of simulation tools (ADAMS software) which permit checking design compatibility with rehabilitation tasks. Two types of rehabilitation exercise in simulation are showed as below, Fig.11(a) and (b) show the finger s flexion exercise and the finger s adduction and abduction exercise. 1) Kinematic Simulation The angular position, velocity are simulated of the robot joints. The simulation time is 5 sec and the values are given as function of the time in Fig.12 (a) and (b). The graph shows that the maximal flexion angle of PIP?MP1?DIP and MP2 joint is 110?90?70? and 20?. This value is in conformance with the design requirements and is also sufficient for normal rehabilitation exercise. 2) Dynamic Simulation At first torques are loaded on the gears of MP1?PIP?DIP and MP2 joint in ADAMS as the CPM machine s driving torque, and the torque value is 0.9Nm?0.1Nm?0.1Nm and 0.8Nm. Second torques are loaded on the finger MP1?PIP?DIP and MP2 joint as the resistance torque, and the torque value is 0.16Nm?0.1Nm?0.1Nm and 0.15Nm. Then the MARK points are created on P1?P2 and P3 finger phalanges before the resultant torques of finger joints are measured. The values are shown in Fig.13. The graphs shows that for MP1?PIP?DIP and MP2 joint, the maximal torque is 0.82Nm?0.21Nm ? 0.31Nm and 0.92Nm, the minimal torque is 0.51Nm?0.20Nm?0.20Nm and 0.60Nm. So during the safety torque range, the CPM machine can drive the finger phalanges to move easily. (a) (b) Fig.11 (a) Schematic diagram of flexion finger, (b) Schematic diagram of adduction and abduction finger 1480 1234 (a) 1234 (b) Fig. 12 (a) Angular position of the DIP(3)?PIP(1)?MP1(2) and MP2(4) joint, (b) Angular velocity of the DIP(3)?PIP(1)?MP1(2) and MP2(4) joint. (a) (b) (c) (d) Fig. 13 (a) Fexion and extension torque of the MP1 joint. (b) Fexion and extension torque of the PIP joint, (c) Fexion and extension torque of the DIP joint, (d) Adduction and abduction torque of the MP2 joint. ?. CONCLUSIONS AND FUTURE WORK Next step we will assemble the other three finger exoskele
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