Elastic Robot Design, Actuation, and Control

In the last decades, robot design shifted from rigid mechanisms towards such with elastic characteristics. A major advantage of mechanics and/or actuation with compliant behavior is improved safety in human-robot interaction.

Besides, such devices enable the exploitation of natural dynamics and can thus distinctly reduce energy requirements. These promising characteristics meet the demands of user-proximal and mobile assistive robotic systems. However, new technical issues emerge as overall system complexity and control requirements increase. Particularly challenging questions need to be answered when considering joint actions of humans and such (assistive) robots.

Our research currently focuses on how elastic robotic actuation can be designed and controlled to be energy-efficient and fault-tolerant. This comprises the configuration of actuator and elastic elements, variable stiffness mechanisms, and the development of control algorithms. Therefore, a complete modeling of the drive train and its interaction with (nonlinear) kinematics are required to understand its natural dynamics. Through system integration, fault-tolerant design, and safety management practical applicability of such actuators is supported. Another aspect of our research is to investigate how compliant characteristics are perceived by humans and how they can be used to support them, e. g., in prosthetic components.

Current Projects Related to this Key Topic:

Sponsored by “Athene Young Investigator” – Program of TU Darmstadt

This project combines methods from engineering and human sciences to tackle the multidisciplinary field of wearable robotic devices for motion support and augmentation.

Through considering human factors in control design, algorithms are envisioned to provide efficient and natural assistance and prevent users‘ from feeling to be “controlled by the device”. Psychophysical exploration of how humans experience the stiffness of wearable robots guides impedance control design. With appropriate adaptation, those algorithms facilitate versatile locomotion types and become fault-tolerant. Additionally, psychometric and human-in-the-loop studies examine the impact of the algorithms on the embodiment of the devices by their users. For practical validation, an adaptive shank prosthesis and a powered knee orthosis are used as wearable robotic demonstrators. Finally, all results inform the specification of a human-oriented control design method to improve user acceptance and satisfaction.

Contact: Philipp Beckerle,

Funded by DFG: BE 5729/1

By integration of elastic components to robotic actuation, the overall system complexity increase and systems are potentially operated in critical states, e.g., (anti)resonances. To handle faults that might emerge from this, the DFG-supported project ‘Fault Diagnosis and Tolerance for Elastic Actuation Systems’ aims at tackling faults in elastically actuated systems by fault diagnosis and fault-tolerant design. For deeper understanding of faults in elastic actuation, structured analysis methods are used and fault diagnosis algorithms as well as tolerance measures are examined in simulations and experiments.

To assess the probability and severity of faults in elastic actuators, we kindly ask interested experts to participate our questionnaire study.

Contact: Florian Stuhlenmiller,

Funded by DFG: BE 5729/2

In cooperation with the Vrije Universiteit Brussel, we investigate the influence of the configuration of actuator and elasticity on the natural dynamics of elastic actuators and their power/energy requirements. For this purpose, rigid as well as serial and parallel elastic configurations are compared in simulations and experiments. Based on the results, conclusions with respect to actuator design and stiffness control are drawn.

Contact: Philipp Beckerle,

Completed Projects Related to this Key Topic:

Funded by DFG: RI 2086/7

This DFG-funded research project aims at the development of concepts and components for adequate user support and provision of feeling of security in dynamic gait situations. A cooperation with the prosthesis manufacturer Blatchford Product Limited, UK, combines expertise of extensive experience in prosthetic development and holistic system architecture mechatronic systems to generate innovative concepts. After performing and analyzing clinical studies with an in-house developed sensor system, concepts for prosthetic components are developed. A holistic mechatronic design methodology integrates gait detection algorithms, control concepts as well as mechanical design and evaluation. After realization of prototypes a validation by test-bench and experimental studies will be done.

Contact: Jochen Schuy,

Picture: IMS

Funded by the TU Darmstadt, this project aimed at active lower limb prostheses which are user-friendly and energy efficient. Human Factors have been analyzed psychologically and integrated into engineering methods to develop user-oriented technologies. To increase energy efficiency, elastic actuation systems and appropriate control algorithms were designed based on simulations of human gait with and without prosthesis.

Contact: Philipp Beckerle,