1234 Part F Field and Service Robotics as haptic simulation of ground conditions (e.g.,stair ing this actuation concept can plausibly execute both climbing). a stiff,position-dominated robot-in-charge mode as An advanced version of the Lokomat integrates force well as a compliant,low-impedance patient-in-charge sensors and automatic adaptation of gait patterns to al- mode. low for a reduction of the interaction effort between A different approach to gait training was taken with patient and machine [53.881.It has been tested on unim- the KineAssist device [53.99].KineAssist is a motor- paired and SCI patients,who were able to influence the ized mobile platform that follows patient and therapist gait trajectories towards a more desired motion by means as they move over ground and incorporates a smart brace of their own motor activity [53.88,94]. that compliantly supports the patient's trunk and pelvis. The pelvic assist manipulator(PAM)is a five-DOF This smart support is designed to allow the therapist to robot for torso manipulation,and the pneumatically adjust its stiffness from fully rigid down to fully com- operated gait orthosis (POGO)is a leg robot with pliant.Within a safety zone,the fully compliant mode two DOFs per leg.PAM's and POGO's actuators are allows patients to challenge the limits of their stabil- pneumatic,which cost less than electric motors and ity.A compliant virtual wall catches the patients when have higher power-to-weight ratios [53.93].The robots'they lose balance.The location of this virtual wall is ability to control forces and yield to patients and/or also adjustable.The body weight can be unloaded as therapists has been tested with unimpaired and SCI needed. patients [53.95].Of particular note here is the devel- Other efforts include Ferris and coworkers [53.100], opment of an adaptive synchronization algorithm that who are developing foot,ankle,knee,and hip orthoses allows these compliant robots to provide assistance at actuated by artificial pneumatic muscles that may pos- 驾 the right time as the patient varies the timing or size of sibly be used to assist in gait training.The Rutgers steps. Ankle is a six-DOF pneumatic system based on a Stew- 53.2 Based on the string-puppet principle,the String-Man art platform that allows exercise of the ankle [53.101]. achieves weight bearing and compliant six-DOF torso Also in the USA,Agrawal's group proposes the use manipulation by means of seven wires and a force sen- of gravity-balancing leg orthoses for people with gait sor on each wire [53.90].In addition,a control scheme impairments to practise walking [53.102].Their de- has been designed for the String-Man to control both signs allow the orthoses to passively support the gravity the zero-moment-point location and the ground reaction torque required at the patient's joints.This approach force with the help of foot force sensors. would have the advantage of being safer than pow- Veneman and colleagues [53.91]are developing ac- erful robots for clinical use.They have also extended tuation systems for robotic exoskeletons that combine their design to include actuators with reduced torque re- Bowden cables with series elastic actuation.The Bow- quirements [53.103].A robot has been used to provide den cables allow the motors to be mounted remotely in graded body weight support as a patient who cannot bear a fixed position,thus reducing the mass to be moved on his full weight because of a medical problem walks in the exoskeleton links.The spring element connecting a circle [53.104]. the Bowden cables with the joint allows the closing of a force feedback control loop with a position sensor that Other Robotic Movement Therapy Approaches measures the spring elongation,a concept inspired from As reviewed above,most of the work to date in the series-elastic actuation concept described by Pratt robotic therapy devices has focused on robots that at- and coworkers [53.96].In addition,series elasticity is tach to patients to assist them in practising reaching useful to reduce the negative effects that static friction or walking exercises.Other early proposals for using and unmodeled dynamics have on the stability of force robots for movement therapy included using two pla- control,thus improving the achievable force control nar robot arms to carefully control continuous passive bandwidth [53.97,98].which is especially important for motion of the knee following joint surgery [53.24]. a Bowden-cable-based system.Series elasticity wors-and using a multi-axis robot arm to place targets for ens positional accuracy,but this is not a critical issue patients doing reaching exercises [53.105].An emerg- for gait-training robots.Veneman's first experimental ing approach toward robotic movement therapy is to results show that adequate force control bandwidth was provide the therapy at a distance,in a form of tele- achieved by a prototype of their Bowden-cable-based rehabilitation,in order to improve accessibility to the actuation design [53.91],so that a robot incorporat- therapy[53.59,106,107.1234 Part F Field and Service Robotics as haptic simulation of ground conditions (e.g., stair climbing). An advanced version of the Lokomat integrates force sensors and automatic adaptation of gait patterns to al￾low for a reduction of the interaction effort between patient and machine [53.88]. It has been tested on unim￾paired and SCI patients, who were able to influence the gait trajectories towards a more desired motion by means of their own motor activity [53.88, 94]. The pelvic assist manipulator (PAM) is a five-DOF robot for torso manipulation, and the pneumatically operated gait orthosis (POGO) is a leg robot with two DOFs per leg. PAM’s and POGO’s actuators are pneumatic, which cost less than electric motors and have higher power-to-weight ratios [53.93]. The robots’ ability to control forces and yield to patients and/or therapists has been tested with unimpaired and SCI patients [53.95]. Of particular note here is the devel￾opment of an adaptive synchronization algorithm that allows these compliant robots to provide assistance at the right time as the patient varies the timing or size of steps. Based on the string-puppet principle, the String-Man achieves weight bearing and compliant six-DOF torso manipulation by means of seven wires and a force sen￾sor on each wire [53.90]. In addition, a control scheme has been designed for the String-Man to control both the zero-moment-point location and the ground reaction force with the help of foot force sensors. Veneman and colleagues [53.91] are developing ac￾tuation systems for robotic exoskeletons that combine Bowden cables with series elastic actuation. The Bow￾den cables allow the motors to be mounted remotely in a fixed position, thus reducing the mass to be moved on the exoskeleton links. The spring element connecting the Bowden cables with the joint allows the closing of a force feedback control loop with a position sensor that measures the spring elongation, a concept inspired from the series-elastic actuation concept described by Pratt and coworkers [53.96]. In addition, series elasticity is useful to reduce the negative effects that static friction and unmodeled dynamics have on the stability of force control, thus improving the achievable force control bandwidth [53.97,98], which is especially important for a Bowden-cable-based system. Series elasticity wors￾ens positional accuracy, but this is not a critical issue for gait-training robots. Veneman’s first experimental results show that adequate force control bandwidth was achieved by a prototype of their Bowden-cable-based actuation design [53.91], so that a robot incorporat￾ing this actuation concept can plausibly execute both a stiff, position-dominated robot-in-charge mode as well as a compliant, low-impedance patient-in-charge mode. A different approach to gait training was taken with the KineAssist device [53.99]. KineAssist is a motor￾ized mobile platform that follows patient and therapist as they move over ground and incorporates a smart brace that compliantly supports the patient’s trunk and pelvis. This smart support is designed to allow the therapist to adjust its stiffness from fully rigid down to fully com￾pliant. Within a safety zone, the fully compliant mode allows patients to challenge the limits of their stabil￾ity. A compliant virtual wall catches the patients when they lose balance. The location of this virtual wall is also adjustable. The body weight can be unloaded as needed. Other efforts include Ferris and coworkers [53.100], who are developing foot, ankle, knee, and hip orthoses actuated by artificial pneumatic muscles that may pos￾sibly be used to assist in gait training. The Rutgers Ankle is a six-DOF pneumatic system based on a Stew￾art platform that allows exercise of the ankle [53.101]. Also in the USA, Agrawal’s group proposes the use of gravity-balancing leg orthoses for people with gait impairments to practise walking [53.102]. Their de￾signs allow the orthoses to passively support the gravity torque required at the patient’s joints. This approach would have the advantage of being safer than pow￾erful robots for clinical use. They have also extended their design to include actuators with reduced torque re￾quirements [53.103]. A robot has been used to provide graded body weight support as a patient who cannot bear his full weight because of a medical problem walks in a circle [53.104]. Other Robotic Movement Therapy Approaches As reviewed above, most of the work to date in robotic therapy devices has focused on robots that at￾tach to patients to assist them in practising reaching or walking exercises. Other early proposals for using robots for movement therapy included using two pla￾nar robot arms to carefully control continuous passive motion of the knee following joint surgery [53.24], and using a multi-axis robot arm to place targets for patients doing reaching exercises [53.105]. An emerg￾ing approach toward robotic movement therapy is to provide the therapy at a distance, in a form of tele￾rehabilitation, in order to improve accessibility to the therapy [53.59, 106, 107]. Part F 53.2