Michigan State University
The robot can achieve the following three performances simultaneously. It can perform continuous steerable jumping that is based on the self-righting and the steering capabilities. Second, the robot only requires a single actuator to perform all the functions. Third, the robot has a light weight to reduce the damage that results from the impact of landing.
Four mechanisms realize the jumping motion sequence. First, the jumping mechanism transforms the stored energy into the robot’s kinetic energy for take-off. Second, the energy mechanism charges the energy and releases it instantly. Third, the self-righting mechanism can have the robot stand up after it lands on the ground. Fourth, the steering mechanism changes the robot’s jumping direction.
For the jumping mechanism, the robot has springs as energy storage medium because they can be implemented with a small weight, and they can be obtained easily at a low cost since they are off-the-shelf components; and good jumping performances can be achieved.
For the jumping mechanism, another energy mechanism is required to store energy and release it when necessary. The approach in this robot rotates the motor in a single direction for energy charge and release, leadingto a short cycle time. This is achieved by a slip-gear system, an eccentric cam, and a variable length crank mechanism. The key element in this mechanism is a one-way bearing. A rotation link is connected to the output shaft of a speed reduction system via a one-way bearing.
Because of the one-way bearing, the rotation link can only rotate in the counter clockwise direction. A cable, which is guided by two pulleys, connects the end of rotation link to the robot’s foot. If the rotation link rotates from the bottom vertical initial position, the cable forces the body to move toward the foot. The rotation link’s top vertical position is a critical position since the torque resulted from the cable will switch its direction. Once the link passes this position, the energy is released, and the body accelerates upward.
With the jumping and energy mechanisms, the robot can jump if it initially stands on the ground with its foot. This case, however, seldom happens due to the landing impact. Therefore, a self-righting mechanism is needed to make the robot recover from possible landing postures. The method used in this robot, is widely used in animals, is the active recovery with actuated parts.
The robot has a rectangular shape with two surfaces significantly larger than the other four. As a result, the robot will contact the ground with one of these two large surfaces most of the time after landing. Two self-righting legs on the body are initially parallel to the two large surfaces. Once actuated, they can rotate simultaneously in opposite directions. After a certain amount of rotation, the robot can stand up for the next jump.
The final mechanism to realize the motion sequence is the steering mechanism, which can change the jumping direction. Based on the robot’s rectangular shape, a steering method without extra actuators has been used.
Two steering gears are placed symmetrically about the motor gear. Both gears are a certain distance away from the robot’s centerline. Since the robot contacts the ground with one of its two large surfaces after landing, one of the two steering gears will touch the ground. Therefore, if the motor rotates, the robot will change its heading direction. The same motor for the other three mechanisms actuates the steering mechanism. The steering mechanism is driven by the motor’s one-directional rotation, while the other three mechanisms are actuated by the other directional rotation. One steering gear is also used in the speed reduction system for energy charge. If the motor rotates in one direction, this gear is used for energy charge. If the motor rotates in the other direction, the rotation link will not rotate due to the one-way bearing. In this case, this gear can steer the robot.
Discuss the mathematical model of the jumping process. Elaborates the mechanical design for the four mechnisms. Performs the optimal design to obtain the best mechanism dimensions. Present the implementation details, experimental results, andcomparison with existing jumping robots.
The dynamics model for mid-air maneuvering is presented. The design for both the mechanical and electrical part is elaborated. Experimental results for the robot’s various functions are presented.