In contrast, humans display significant trunk motions that follow the natural dynamics of the gait. Related work mostly focuses on the lower extremities, and simplifies the problem by stabilizing the trunk at a fixed angle. The research on trunk movements in human locomotion is insufficient, and no formalism is known to transfer human motion patterns onto robots. We conclude that the magnitude of torque and power required to reduce hypermetria by simple wearable assistive devices may be significantly underestimated if muscle-tendon characteristics are not considered.Ĭreating natural-looking running gaits for humanoid robots is a complex task due to the underactuated degree of freedom in the trunk, which makes the motion planning and control difficult. We found that-depending on the type of assistance-the predicted torques and powers can differ by more than a factor of 10 between musculoskeletal and torque-driven arm models. We implemented mechanical and low-level assistive torque strategies in simulation which lead to a reduction of hypermetria. By introducing inconsistent neuronal control parameters, we induced hypermetria.
To test this, we simulated two-degree-of-freedom point-to-point arm movements.
As musculoskeletal dynamics play an important role in the interaction between an assistive device and the neuro-musculoskeletal system, we hypothesized that their consideration in the model might influence the predicted design parameters. This work focuses on the idea of compensating hypermetria (overshoot)-a motor control deficit that may occur in neurodegenerative diseases-by a simple assistive device. Models of the human arm may help to estimate design parameters like peak torque and power of wearable assistive devices by predicting required forces to compensate for motor control impairments. By tuning SELDA's activation timing, we effectively adjust the robot's hopping height by 11% and its forward velocity by 14%, even with comparatively low power injection to the distal joint.
We compare two leg configurations controlled by a central pattern generator that both feature agile forward hopping. We develop, implement, and characterize a bioinspired robot leg that features a SELDA-actuated foot segment.
With this goal in mind, we propose a low-friction, lightweight Series ELastic Diaphragm distal Actuator (SELDA) which meets many, although not all, of the above requirements. Ideally, such an actuator can be controlled directly and without mechanical cross-coupling, for example remotely. So far no designs are available that feature all characteristics of a perfect distal legged locomotion actuator a low-weight and low-inertia design, with high mechanical efficiency, no stick and sliding friction, low mechanical complexity, high-power output while being easy to mount. But unlike robots, animals achieve series elastic actuation by their muscle-tendon units. Animals' anatomy and locomotion capabilities emphasize the importance of that lightweight legs and integrated, compact, series elastically actuated for distal leg joints. Robots need lightweight legs for agile locomotion, and intrinsic series elastic compliance has proven to be a major ingredient for energy-efficient locomotion and robust locomotion control.
We found differences between all three configurations the Soleus spring-tendon modulates the robot’s speed and energy efficiency likely by ankle power amplification, while the Gastrocnemius spring-tendon changes the movement coordination between knee and ankle joints during push-off.ĭata-cad-code VideoYT pdf link (url) DOI Share We controlled the robot with a feed-forward central pattern generator, leading to walking speeds between 0.35 m/s and 0.57 m/s at 1.0 Hz locomotion frequency, at 0.35 m leg length. We tested the influence of three Soleus and Gastrocnemius spring-tendon configurations on the ankle power curves, the coordination of the ankle and knee joint movements, the total cost of transport, and walking speed. We developed a 0.49 m tall, 2.2 kg anthropomorphic bipedal robot with Soleus and Gastrocnemius muscle-tendon units represented by linear springs, acting as mono- and biarticular elastic structures around the robot’s ankle and knee joints. Legged robots allow testing the interaction between complex leg mechanics, control, and environment in real-world walking gait. However, the mechanics of the human’s lower leg with its complex muscle-tendon units spanning over single and multiple joints is not yet understood.
One mechanism that is assumed to contribute to the high efficiency of human walking is the impulsive ankle push-off, which potentially powers the swing leg catapult. Legged locomotion in humans is governed by natural dynamics of the human body and neural control.