This paper presents the final realization of a supportive robotic device for repetitive sit-to-stand (StS) training for stroke victims as well as for the elderly persons. The sit-to-stand process belongs to the activities of daily living (ADL) and is conducted several hundred times per day by the average healthy human. Regaining the ability to rise thus is an important aspect for the quality of life and self-dependence and has to be trained – after stroke as well as for the elderly. The motivation is to develop supportive robots and devices to relieve physiotherapists, such that the robot takes over the physical demanding tasks, i.e. lifting a patient or moving the limbs, while the physiotherapist is able to focus on cognitive interaction and encouragement.

An important property of rehabilitation robots required for safe and human-like interaction is compliant actuation combined with light-weight design. This requirement can be fulfilled by fluidic soft-actuators like pneumatic muscles due to inherent passive compliancy and high power to weight ratio. However because of the nonlinear dependency on actuator chamber contraction and air pressure as well as friction effects control of such actuator type still remains challenging, even for common position or force control. For human-robot-interaction (HRI) it is necessary to adapt the actuator output characteristics appropriately depending on the manipulation task and/or the capabilities of the individual person. This paper presents an approach to independently adjust torque and compliance/stiffness of a soft-actuator with direct acting antagonistic rotary elastic chambers (REC) and illustrates a possible example of application with an exoskeleton robot for lower extremities training.

The purpose of this paper is to present a concept of human-robot-interaction control for robots with compliant pneumatic soft-actuators which are directly attached to the human body. Backdrivability of this type of actuators is beneficial for comfort and safety and they are well suitable to design rehabilitation robots for training of activities of daily living (ADL). The concept is verified with an application example of sit-to-stand tasks taking conventional treatment in neurology as reference. The focus is on stroke patients with a target group suffering from hemiplegia and paralysis in one half of the body. A 2 DOF exoskeleton robot was used as testbed to implement the control concept for supporting rising based on a master-slave position control such that movements from the fit leg are transferred to the affected leg. Furthermore the wearer of the robot has the possibility to adjust support for stabilizing the knee joint manually. Preliminary results are presented.

This paper presents a concept for human-robot-interaction (HRI) for controlling robots with compliant pneumatic soft-actuators which are directly attached to the human body. For comfort and safety backdrivability of this type of actuators is beneficial and they are well suitable to design rehabilitation robots. As application example for training of activities of daily living (ADL) sit-to-stand tasks are used, taking conventional treatment in neurology as reference. The focus is on stroke patients with a target group suffering from hemiplegia and paralysis in one half of the body. Based on master-slave position control movements form the fit leg are transferred to the affected led using a 2 degrees of freedom (DOF) exoskeleton robot as testbed. Furthermore the wearer of the robot has the possibility to adjust support for stabilizing the knee joint manually.

Inherent compliance and assistive behavior are assumed to be essential properties for safe human-robot interaction. Rehabilitation robots demand the highest standards in this respect because the machine interacts directly with weak persons who are often sensitive to pain. Using novel soft fluidic actuators with rotary elastic chambers (REC actuators), compact, lightweight, and cost-effective therapeutic devices can be developed. This article describes modular design and control strategies for new assistive acting robotic devices for upper and lower extremities. Due to the inherent compliance and natural back-drivability of pneumatic REC actuators, these movement therapy devices provide gentle treatment, whereby the interaction forces between humans and the therapy device are estimated without the use of expensive force/torque sensors. An active model-based gravity compensation based on separated models of the robot and of the individual patient’s extremity provides the basis for effective assistive control. The utilization of pneumatic actuators demands a special safety concept, which is merged with control algorithms to provide a sufficient level of safeness and to catch any possible system errors and/or emergency situations. A self-explanatory user interface allows for easy, intuitive handling. Prototypes are very comfortable for use due to several control routines that work in the background. Assistive devices have been tested extensively with several healthy persons; the knee/hip movement therapy device is now under clinical trials at the Clinic for Orthopaedics and Trauma Surgery at the Klinikum Stuttgart.

Compactness, passive (inherent) compliance and low weight are the most important benefits of pneumatic soft-actuators with rotary elastic chambers (REC-actuators). Robots with these natural back-drivable actuators are well suitable for safe physical interaction tasks especially in service and rehabilitation, where human and robots operate in direct contact. In this paper the application of different control strategies for physical interaction of pneumatic soft-robots is considered. For control feedback the current measurements of pressure and joint angle position as well as a force/torque observer based on inverted experimental torque characteristics of the REC-actuators are utilized. An adaptive admittance control with trajectory modification (ACTM) is compared by simulation to an adaptive admittance control with variable stiffness regulation (ACSR) using a model of a planar robot with two rotary joints. Both concepts enable desired force tracking in constraint direction and compliant position control in unconstraint direction. Furthermore the more promising ACSR approach was implemented and validated within an experimental setup using a planar soft-robot with two REC-actuators by tracking even or lightly curved surfaces without knowledge of the environment parameters.

Compliance and assistive behavior are essential properties for safe physical human-robot interaction (HRI), an illustrative example for which is robot aided motion therapy. These requirements can be easily fulfilled using inherent compliant and back-drivable (i.e. soft) actuators. This paper describes a fully functional prototype for assistive robotic knee MTD with novel inherent compliant (soft) fluidic actuators of rotary type, which has been developed for orthopedic rehabilitation purposes. Assistive acting motion therapy devices (MTD) are mainly used for neurologic treatment until now, but become increasingly important for orthopedic rehabilitation as well. Device capabilities provide human-like treatment and allow individual adjustable assistance to accomplish desired motions. Utilization of pneumatic soft-actuators demands a special safety concept which is merged with control algorithms to provide sufficient safeness and to catch any possible system errors and sudden emergency situations. A self descriptive user interface allows easy intuitive handling and the prototype can be used very comfortable due to several imperceptible working routines in the background. The same safety and handling concept is used for assistive robotic shoulder MTD, which is currently being developed.

Robot assisted motion therapy attains increasingly importance and acceptance especially in neurorehabilitation after stroke or spinal injury, but also in orthopedic rehabilitation and surgical interventions. Several studies have shown that a patient-cooperative (assistive) motion therapy, which activates remaining muscle strength and so optimizes recovery, will cause a much higher effectiveness compared to commonly used continuous passive motion (CPM) machines with pre-programmed trajectories (motion profiles). This article describes an assistive control concept developed for orthopedic rehabilitation based on inherent compliant (soft) actuators. Control concept takes into acccount specific properties of physiotherapists behavior during treatment. The patient will be supported and at the same time encouraged to generate own muscular strength to perform desired movement. Concept has been implemented for two prototypes of motion therapy devices (MTD) for knee and shoulder motion therapy. The first prototype (Knee-MTD) has been extensively tested with healthy persons and now is being tested in the Clinic for Orthopaedics and Trauma Surgery of Klinikum Stuttgart to prove concept in real-life conditions.