Gijs van Oort

LOPES II—Design and Evaluation of an Admittance Controlled Gait Training Robot With Shadow-Leg Approach

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.

An energy efficient knee locking mechanism for a dynamically walking robot

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 four-bar 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.

Compact analysis of 3D bipedal gait using geometric dynamics of simplified models

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.

Performance Comparison of a Planar Bipedal Robot with Rigid and Compliant Legs

The purpose of this work is to study the effect of placing passive storage elements (springs) along the robot legs on its performance. We first present the model of a planar passive dynamic walker with compliant ground contact model, then replace its rigid legs with compliant legs. Simulation results validate the effectiveness of compliant legs in improving the performance (robustness and velocity) of the robot.

New Ankle Actuation Mechanism for a Humanoid Robot

In this article we discuss the design of a new ankle actuation mechanism for the humanoid robot TUlip. The new mechanism consists of two coupled series-elastic systems. We discuss the choice of actuators according to calculations for maximum achievable walking speed. Some control issues, MIMO and non-linearities are also discussed.