One of the main challenges of the active assistive devices is how to estimate the motion of the missing/impaired limbs and joints in line with the remaining limbs. To do so, a motion planner is required. This study proposes a motion planner that can be used for active prosthetic/orthotic knees. The aim is to continuously estimate the knee joint positions based on the thigh motion, using as few inputs as possible. Data from thigh-mounted IMU (thigh acceleration and angle) are used as inputs to estimate knee joint positions as outputs. It is aimed to continuously estimate the outputs as opposed to the state-machine approaches which divide the gait cycles into different sections and require switching rules. The performance of the motion planner is investigated for five walking speeds (0.6, 0.9, 1.2, 1.4 and 1.6 m/s). The strengths and limitations of the motion planer are investigated at different scenarios.

Elastic elements in prosthetic devices can help to reduce peak power (PP) and energy requirements (ER) for the actuators. Calculations showed that it is impossible with current commercial motor technology to mimic human ankle behavior in detail for higher walking and running speeds with single motor solutions using a Serial Elastic Actuator (SEA). Concerning this result we checked the requirements of a parallel elastic actuator (PEA) and a combination of serial and parallel (SE+PEA) springs. We found that a PEA can reduce PP additionally in comparison to the SEA by pre-loading the spring in the flight phase. This reduces also peak torque. But this loading needs additional energy so that the ER increase in comparison to the SEA. The SE+PEA concept can further decrease PP. With that, the ER are less than the PEA but higher than for the SEA. The results show less benefit for the PEA and the SE+PEA when a constant stiffness and a fixed parallel spring slack length is used for both gaits and all speeds. All concepts show that mimicking human ankle joint behavior in running and walking at higher speeds is still challenging for single motor devices.

In this paper, a suspended mobile platform with two 3 DOF manipulators, is used to manipulate an object in a combined circular-straight path. The multiple impedance control (MIC) is used as a model-based algorithm which has been shown to have desirable performance in case of impact with an obstacle and system flexibility. The MIC enforces same impedance law both on the robotic system, and the manipulated object level. However, to apply model-based control laws, it is needed to extract system dynamics model. For such complicated robotic systems with suspension system, it is necessary to have a concise set of dynamic equations of motion with few mathematical calculations. Therefore, the concept of direct path method is extended to derive explicit dynamics modeling for such challenging systems. Then, non-holonomic constraint of the wheeled system is derived, and the obtained dynamics model is reformatted to become a more concise one using natural orthogonal complement method. Next, the MIC law is applied to cooperative manipulation of an object by two manipulators mounted on a suspended wheeled robotic system. The obtained results reveal a smooth system performance, i.e. negligible small tracking errors in the presence of impacts with obstacles and significant disturbances.