Balance capacity is necessary for young people as well as for elderly people. In particular, athletes need balancing abilities to prevent sudden injuries and maximize their athletic performance. A robot for balance training is proposed as shown in the figure 1.
Virtual Ground is divided into creating a geometric posture and a spatial impedance. Geometric postures are implemented by changing the elevation of height and tilt of the ground slope as shown in figure 2. For spatial impedance implementation of the ground, the person should feel as if the spring and the damper are placed under the ground. Depending on the variation in the spring and the damper value, the person can feel hard or soft in the ground.
Figure 3 shows a picture of the proposed Virtual Ground Robot(VGR), which also shows the configuration of it: VGR is driven by three legs, each of which consists of two revolute joints that are connected to the lower base and one spherical joint that is connected with the upper plate (3-RRS). Three RRS legs are equally spaced at the angle of 120 degrees so that the whole robot can generate three- degree-of-freedom motions in the pitch, the roll, and the vertical Z-axis direction.
The most significant features of the proposed VGR are that 1) it is driven by RFSEAs, and thus it can provide precise forces and torques, 2) the size of the VGR is small enough for a human to stand on with ease, and 3) it can generate torque/force large to support a weight of a human.
The virtual environment that is generated by VGR can provide virtual experiences and excitation to humans. Human characteristics can be measured by using VGR. Through the VGR, the interaction and the motion of human beings and robots is measured in real time. This can be important data to understand and analyze human characteristic with regard to virtual excitation. Also, it can be possible to suggest comprehensive evaluation index of the physical ability of a person by creating a data base while accumulating human characteristic data.