Hao Dabin

Hopping movement simulation of elastic actuator

In this paper, we presented a multimodal elastic actuator which combining the motor, spring, brake and clutch that produces several modes of operation. The operation modes including stiff position control, series elastic actuation as well as the possibility to store and release energy were analyzed. A prototype of multimodal elastic actuator was constructed, dynamics equations of elastic actuator were established, and hopping movements with harmonic excitation were studied. Hopping movement was analyzed using receding horizon policy, the elastic actuator was controlled with preloaded hopping, and the hopping simulations with different ground trajectories were studied. The hopping movement simulation study of multimode elastic actuator provides important theoretical basis for the understanding of motion mechanism of bionic actuator and control implementation of hopping movement.

The study of multimodal series elastic actuator

An elastic actuator is proposed for meeting the knee power-assisted exoskeleton effective drive demand under different walking pattern. The actuator can achieve different motion of power-assisted knee exoskeleton through the motor driving the screw nut, series with spring and combing with the corresponding brake pads, and the motion modes are analyzed. The kinematics equations of elastic actuator were established, and the effects of spring stiffness and damping for the properties of elastic actuator are studied. The prototype of actuator is designed and tested, and braking force and motion following experiments are implanted. The results of experiments showed that the elastic actuator can realize effective braking force and favorable motion following. The study of multi-mode elastic actuator provides important theoretical basis for the understanding of motion mechanism of bionic actuator.

The Energy Amplification Characteristic Research of a Multimodal Actuator

A multimodal actuator is proposed to fulfil the different walking patterns of a power-assisted knee exoskeleton. With this actuator, the exoskeleton leg can realize several modes of operation, including series elastic actuation, stiff position control and energy storage and release. The energy amplification characteristics of the multimodal actuator in the series elastic mode are analysed. A dynamics model was established to study how series elasticity and the equivalent mass of transmission influence a power source, such as an electric motor. The results, in both simulation and experiment, show that series elasticity can amplify actuator power output, and the power output of a multimodal actuator is greater when the equivalent mass of the transmission mechanism is smaller. This research into multimodal actuator energy amplification supplies important insights into the design of artificial systems that can more closely approximate the performance of biological systems.