The existing shortage of therapists and caregivers assisting physically disabled individuals at home is expected to increase and become serious problem in the near future The patient population needing physical rehabilitation of the upper extremity is also constantly increasing Robotic devices have the potential to address this problem as noted by the results of recent research studies However, the availability of these devices in clinical settings is limited, leaving plenty of room for improvement The purpose of this paper is to document a review of robotic devices for upper limb rehabilitation including those in developing phase in order to provide a comprehensive reference about existing solutions and facilitate the development of new and improved devices In particular the following issues are discussed: application field, target group, type of assistance, mechanical design, control strategy and clinical evaluation This paper also includes a comprehensive, tabulated comparison of technical solutions implemented in various systems

/pdf/a-survey-on-robotic-devices-for-upper-limb-rehabilitation-3ykq953s17.pdf

A survey on robotic devices for upper limb rehabilitation

The existing shortage of therapists and caregivers assisting physically disabled individuals at home is expected to increase and become serious problem in the near future. The patient population needing physical rehabilitation of the upper extremity is also constantly increasing. Robotic devices have the potential to address this problem as noted by the results of recent research studies. However, the availability of these devices in clinical settings is limited, leaving plenty of room for improvement. The purpose of this paper is to document a review of robotic devices for upper limb rehabilitation including those in developing phase in order to provide a comprehensive reference about existing solutions and facilitate the development of new and improved devices. In particular the following issues are discussed: application field, target group, type of assistance, mechanical design, control strategy and clinical evaluation. This paper also includes a comprehensive, tabulated comparison of technical solutions implemented in various systems.

A survey on robotic devices for upper limb

Based on evidence from recent experiments in motor learning and neurorehabilitation, we hypothesize that three desirable features for a controller for robot-aided movement training following stroke are high mechanical compliance, the ability to assist patients in completing desired movements, and the ability to provide only the minimum assistance necessary. This paper presents a novel controller that successfully exhibits these characteristics. The controller uses a standard model-based, adaptive control approach in order to learn the patient's abilities and assist in completing movements while remaining compliant. Assistance-as-needed is achieved by adding a novel force reducing term to the adaptive control law, which decays the force output from the robot when errors in task execution are small. Several tests are presented using the upper extremity robotic therapy device named Pneu-WREX to evaluate the performance of the adaptive, ldquoassist-as-neededrdquo controller with people who have suffered a stroke. The results of these experiments illustrate the ldquoslackingrdquo behavior of human motor control: given the opportunity, the human patient will reduce his or her output, letting the robotic device do the work for it. The experiments also demonstrate how including the ldquoassist-as-neededrdquo modification in the controller increases participation from the motor system.

/pdf/optimizing-compliant-model-based-robotic-assistance-to-1g1esjc2bz.pdf

Optimizing Compliant, Model-Based Robotic Assistance to Promote Neurorehabilitation

We describe the design and control of a wearable robotic device powered by pneumatic artificial muscle actuators for use in ankle–foot rehabilitation. The design is inspired by the biological musculoskeletal system of the human foot and lower leg, mimicking the morphology and the functionality of the biological muscle–tendon–ligament structure. A key feature of the device is its soft structure that provides active assistance without restricting natural degrees of freedom at the ankle joint. Four pneumatic artificial muscles assist dorsiflexion and plantarflexion as well as inversion and eversion. The prototype is also equipped with various embedded sensors for gait pattern analysis. For the subject tested, the prototype is capable of generating an ankle range of motion of 27 ◦ (14 ◦ dorsiflexion and 13 ◦ plantarflexion). The controllability of the system is experimentally demonstrated using a linear time-invariant (LTI) controller. The controller is found using an identified LTI model of the system, resulting from the interaction of the soft orthotic device with a human leg, and model-based classical control design techniques. The suitability of the proposed control strategy is demonstrated with several angle-reference following experiments.

/pdf/design-and-control-of-a-bio-inspired-soft-wearable-robotic-110pb507k2.pdf

Design and control of a bio-inspired soft wearable robotic device for ankle-foot rehabilitation.

Consider a given dynamical system, described by ẋ = f(x) (wheref is a nonlinear function) and [x0] a subset ofR. We present an algorithm, based on interval analysis, able to show that there exists a unique equilibrium statex∞ ∈ [x0] which is asymptotically stable. The effective method also provides a set[x] (subset of[x0]) which is included in the attraction domain of x∞.

Ieee transactions on automatic control

A control law is developed for an inexpensive pneumatic motion control system using four solenoid on/off valves and a position feedback sensor. A sliding-mode approach is used, which is well known for its tolerance for system uncertainties. In contrast to previous control laws, our approach does not use pulsewidth modulation. The control law has an energy-saving mode that saves electrical power, reduces chattering, and prolongs the valve's life. Our simulation and experimental results show that the proposed tracking control law performs very well with good tracking and relatively low steady-state position errors

/pdf/accurate-sliding-mode-control-of-pneumatic-systems-using-low-327f2l68h3.pdf

Accurate Sliding-Mode Control of Pneumatic Systems Using Low-Cost Solenoid Valves

In this paper, a state estimation technique is developed for sensing inclination angles using low-cost sensors. A low-bandwidth tilt sensor is used along with an inaccurate rate gyro and a low-cost accelerometer to obtain the measurement. The rate gyro has an inherent bias along with sensor noise. The tilt sensor uses an internal pendulum and therefore has its own slow dynamics. These sensor dynamics were identified experimentally and combined to achieve high-bandwidth measurements using an optimal linear state estimator. Potential uses of the measurement technique range from robotics, to rehabilitation, to vehicle control.

High bandwidth tilt measurement using low-cost sensors

A key challenge in rehabilitation robotics is the development of a lightweight, large force, high degrees-of-freedom device that can assist in functional rehabilitation of the arm. Pneumatic actuators can potentially help meet this challenge because of their high power-to-weight ratio. They are currently not widely used for rehabilitation robotics because they are difficult to control. This paper describes the control development of a pneumatically actuated, upper extremity orthosis for rehabilitation after stroke. To provide the sensing needed for good pneumatic control, position and velocity of the robot are estimated by a unique implementation of a Kalman filter using MEMS accelerometers. To compensate for the nonlinear behavior of the pneumatic servovalves, force control is achieved using a new method for air flow mapping using experimentally measured data in a least-squares regression. To help patients move with an inherently compliant robot, a high level controller that assists only as needed in reaching exercises is developed. This high level controller differs from traditional trajectory-based, position controllers, allowing free voluntary movements toward a target while resisting movements away from the target. When the target cannot be reached voluntarily, the controller slowly builds up force, pushing the arm toward the target. As each target position is reached, the controller builds an internal model of the subject's capability, learning the forces necessary to complete movements. Preliminary testing performed on a non-disabled subject demonstrated the ability of the orthosis to complete reaching movements with graded assistance and to adapt to the effort level of the subject. Thus, the orthosis is a promising tool for upper extremity rehabilitation after stroke.

/pdf/control-of-a-pneumatic-orthosis-for-upper-extremity-stroke-225yc4npnt.pdf

Control of a pneumatic orthosis for upper extremity stroke rehabilitation.

Because of many advantages over other control systems, semi-active control devices have received considerable attention for applications to civil infrastructures. A variety of different semi-active control devices have been studied for applications to buildings and bridges subject to strong winds and earthquakes. Recently, a new semi-active control device, referred to as the resetable semi-active stiffness damper (RSASD), has been proposed and studied at the University of California, Irvine (UCI). It has been demonstrated by simulation results that such a RSASD is quite effective in protecting civil engineering structures against earthquakes, including detrimental near-field earthquakes. In this paper, full-scale hardware for RSASD is designed and manufactured using pressurized gas. Experimental tests on full-scale RSASDs have been conducted to verify the hysteretic behaviours (energy dissipation characteristics) and the relation between the damper stiffness and the gas pressure. The correlation between the experimental results of the hysteresis loops of RASADs and that of the theoretical ones has been assessed qualitatively. Experimental results further show the linear relation between the gas pressure and the stiffness of the RSASD as theoretically predicted. Finally, shake table tests have also been conducted using an almost full-scale 3-storey steel frame model equipped with full-scale RSASDs at the National Center for Research on Earthquake Engineering (NCREE), Taipei, Taiwan, and the results are presented. Experimental results demonstrate the performance of RSASDs in reducing the responses of the large-scale building model subject to several near-field earthquakes. Copyright © 2007 John Wiley & Sons, Ltd.

Full-scale experimental verification of resetable semi-active stiffness dampers

A state estimation technique is developed for sensing inclination angles using relatively low cost sensors. A low bandwidth tilt sensor is used along with an inaccurate rate gyro to obtain the measurement. The rate gyro has an inherent bias along with sensor noise. The tilt sensor uses an internal pendulum and therefore has its own slow dynamics. These sensor dynamics were identified experimentally and combined to achieve high bandwidth measurements using an optimal linear state estimator. Potential uses of the measurement technique range from robotics, to rehabilitation, to vehicle control.

/pdf/bandwidth-tilt-measurement-using-low-cost-sensors-4gt97mq5wv.pdf

J. Leavitt

Papers

Accurate Sliding-Mode Control of Pneumatic Systems Using Low-Cost Solenoid Valves

High bandwidth tilt measurement using low-cost sensors

Control of a pneumatic orthosis for upper extremity stroke rehabilitation.

Full-scale experimental verification of resetable semi-active stiffness dampers

Bandwidth tilt measurement using low cost sensors