Theoretical and experimental research of the vertical dynamic of an electric wheelchair and optimizing the ride comfort using semi-active dampers

Within the scope of the BMWi-sponsored ZIM-project LoCoMs (Low-Cost Mechatronic Systems), analytical tools are being developed on the basis of mechatronic design methodology that allow for the efficient design of mechatronic systems. One example for the application for the project results is the reduction of vertical vibrations of an electric wheelchair (AVC – Active Vibration Control). In this case, the aim is to reduce the whole body vibrations during the ride by the exchange of passive damping elements through controllable semi-active ones. For the experimental analysis in time and frequency domain, the wheelchair has been equipped with accelerometers. Furthermore, a test stand that enables the quasi-harmonic stimulation in vertical direction (0 Hz – 30Hz, ±5mm) on a wheel through the use of an eccentric has been constructed and realized. To create realistic and reproducible measurement a DIN-certified dummy (DIN 45676) has been created to emulate the mechanic input impedance of the human body. The evaluation of the vibrations is calculated in compliance with the ISO 2631-1 (human vibration). For the mechatronic design, a multi-body system of the wheelchair has been created in SIMPACK, while the determination of stiffness and dampening of the wheels has been determined experimentally. In this contribution, results of measurements of the wheelchair on the test stand and the simulated calculations in frequency domain will be presented. At first, the model will be used to determine the parameters of the optimized spring-damper-element in various driving and operating conditions. In a second step, passive damping elements will be replaced by semi-active ones. The regulation of the controllable damper will happen in line with a co-simulation between SIMPACK and MATLAB/Simulink. This enables the gauging of the efficiency of the model's various control algorithms connected to the semi-active dampers; the findings can later be used for the realization on the real wheelchair. Parallel to the simulation calculations, the real wheelchair will be enlarged by the integration of controllable electro-rheologic damping elements and the installation of a mechatronic system to improve the driving comfort in the next stage of the project.