Overcoming hurdles – efficiency and performance on two legs

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In technical bipedal robots, the system's natural dynamics can be adjusted to achieve high energy efficiency by tuning mechanical components of the system, such as springs and dampers in the form of compliant mechanisms. The increased efficiency allows for the use of smaller actuators, which further reduces losses in the drivetrains. However, due to this downsizing, such highly specialized systems cannot perform movements like jumps, which require very high power for a short time. High jumps and long jumps, however, are fundamental movements for bipedal walking systems that are supposed to overcome obstacles. However, these jumping movements occur only sporadically. Hence, the required power for them can be provided once by discharging a mechanical energy store (preloaded springs). Since compliant mechanisms are already integrated into the robot system in order to optimize the natural dynamics, the aim is to use them as an energy store when performing jumps. Walking systems that use compliant mechanisms both to optimize the natural dynamics and efficiency of walking and as energy storage for high-performance jumps are not known from the literature. Therefore, the goal of the proposed project is to provide the scientific basis that will advance the integration and design of compliant mechanisms for both walking efficiency and jump performance. To this end, the compliant mechanisms will specifically use nonlinear characteristics to passively or semi-actively switch between different operating modes during operation. The movements of a bipedal walker are investigated in a model-based manner. The compliant mechanisms are described by kinematic and dynamic models. A motion model of the bipedal walker that includes compliant mechanisms is used on the one hand as a basis for simulations for the development and optimization of the overall system; on the other hand, it is the basis for upgrading and controlling an existing prototype on which the developed mechanisms are validated. The application of the results is possible where energy-efficient walking and overcoming obstacles is considered a prerequisite, for example in extra-terrestrial walking systems or in long rescue missions. In addition, the methods can be used to realize new characteristics and to switch between them economically (preferably without energy). The results of the investigation to be obtained can be used for other technical systems where new complex characteristic curves and the ability to switch from one characteristic curve to another, especially in an energy-free way, are required.