Hopping Robot Using Variable Structured Elastic Actuators

In this paper, we focus on the validity of using a Variable Structured Elastic Actuator (VSEA) for a hopping robot. A VSEA is proposed by Miura and Katsura. The VSEA is composed of an electromagnetic clutch, springs, a geared motor, and a load. The clutch connects the output of the geared motor and the load. The spring is installed between the load and motor housing. By changing the clutch current, the clutch system can mechanically separate the geared motor and the output. A VSEA has a structure similar to a Parallel Elastic Actuator (PEA) in which a spring and gear motor are connected in parallel when a clutch is connected. By disconnecting the clutch, gear friction can be ignored and high power and high-speed motion on the output side are possible. High power and high-speed operation are important factors in hopping motion, and the spring energy was efficiently extracted by using the clutch, and continuous hopping was realized by adjusting the timing of enabling/disabling the clutch. We performed three experiments. The first experiment showed that a VSEA enables a robot to hop higher than a robot including a PEA. The second experiment examined energy efficiency and showed the effectiveness of the robot including the VSEA. The third experiment showed that continuous hopping was possible using the proposed hopping control. From the above, the proposed VSEA robot is effective for efficient hopping motion.