Robotic gait training is gaining ground in rehabilitation. Room for improvement lies in reducing donning and doffing time, making training more task specific and facilitating active balance control, and by allowing movement in more degrees of freedom. Our goal was to design and evaluate a robot that incorporates these improvements. LOPES II uses an end-effector approach with parallel actuation and a minimum amount of clamps. LOPES II has eight powered degrees of freedom (hip flexion/extension, hip abduction/adduction, knee flexion/extension, pelvis forward/aft and pelvis mediolateral). All other degrees of freedom can be left free and pelvis frontal- and transversal rotation can be constrained. Furthermore arm swing is unhindered. The end-effector approach eliminates the need for exact alignment, which results in a donning time of 10-14 min for first-time training and 5-8 min for recurring training. LOPES II is admittance controlled, which allows for the control over the complete spectrum from low to high impedance. When the powered degrees of freedom are set to minimal impedance, walking in the device resembles free walking, which is an important requisite to allow task-specific training. We demonstrated that LOPES II can provide sufficient support to let severely affected patients walk and that we can provide selective support to impaired aspects of gait of mildly affected patients.

In this paper, we present the design, control, and preliminary evaluation of the Symbitron exoskeleton, a lower limb modular exoskeleton developed for people with a spinal cord injury. The mechanical and electrical configuration and the controller can be personalized to accommodate differences in impairments among individuals with spinal cord injuries (SCI). In hardware, this personalization is accomplished by a modular approach that allows the reconfiguration of a lowerlimb exoskeleton with ultimately eight powered series actuated (SEA) joints and high fidelity torque control. For SCI individuals with an incomplete lesion and sufficient hip control, we applied a trajectory-free neuromuscular control (NMC) strategy and used the exoskeleton in the ankle-knee configuration. For complete SCI individuals, we used a combination of a NMC and an impedance based trajectory tracking strategy with the exoskeleton in the ankle-knee-hip configuration. Results of a preliminary evaluation of the developed hardware and software showed that SCI individuals with an incomplete lesion could naturally vary their walking speed and step length and walked faster compared to walking without the device. SCI individuals with a complete lesion, who could not walk without support, were able to walk with the device and with the support of crutches that included a push-button for step initiationOur results demonstrate that an exoskeleton with modular hardware and control allows SCI individuals with limited or no lower limb function to receive tailored support and regain mobility.

In this paper a novel concept of embedded robotic actuator is presented which has been named the Very Versatile Energy Efficient (V2E2) actuator. This actuator stores energy during any force profile which generates negative work on the load and it does therefore have unprecedented potentials for robotics applications.

This paper presents an experimental study on balance recovery control with a lower limb exoskeleton robot. Four participants were subjected to a perturbation during standing, a forward force impulse applied to their pelvis that forced them to step forward with the right leg for balance recovery. Trials with and without exoskeleton assistance to move the stepping legs thigh were conducted to investigate the influence of the exoskeletons control assistance on balancing performance and a potential adaptation. Analysis of the body kinematics and muscle activation demonstrates that robotic assistance: (1) was easy to use and did not require learning, nor inhibited the healthy stepping behavior; (2) it modified the stepping leg trajectories by increasing hip and knee movement; (3) increased reaction speed and decreased the step duration, (4) generally increased biceps femoris and rectus femoris muscle activity.

In this work, we present the design and the implementation of an innovative knee locking mechanism for a dynamically walking robot. The mechanism consists of a fourbar linkage that realizes a mechanical singularity for locking the knee when the leg is in the extended position. Once extended, the knee remains locked without energy consumption, while unlocking it only costs a small amount of energy. Tests showed that the robot walks robustly and that the energy consumption of the new system is low.

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Abstract-The large number of degrees of freedom in legged robots give rise to complicated dynamics equations. Analyzing these equations or using them for control can therefore be a difficult and non-intuitive task. A simplification of the complex multi-body dynamics can be achieved by instantaneously reducing it to an equivalent single inertial entity called the locked inertia or the composite rigid body inertia.In this paper, we adopt the methods of geometric dynamics to analyze the gait using the locked inertia of the robot. The analysis includes the rolling of a biped on a 3D rigid foot and 3D impacts. An example of numerical optimization of foot shape parameters is shown.Our long-term objective is to develop the theoretical framework and to provide the necessary tools for systematic analysis, design, and control of efficient biped robots.

Most active upper-extremity rehabilitation exoskeleton designs incorporate a three sequential rotational shoulder joint with orthogonal axes. This kind of joint has poor conditioning close to singular configurations when all joint axes become coplanar, which reduces its effective range of motion. We investigate an alternative approach of using a redundant non-orthogonal 4R shoulder joint. By inspecting the behavior of the possible nullspace motions, a new method is devised to resolve the redundancy in the differential inverse kinematics (IK) problem. A 1D nullspace global attraction method is used, instead of naive nullspace projection, to guarantee proper convergence. The design of the exoskeleton and the proposed IK method ensure good conditioning, avoid collisions with the human head, arm and trunk, can reach the entire human workspace, and outperforms conventional 3R orthogonal exoskeleton designs in terms of lower joint velocities and no body collisions.