In this paper, we study cooperative control problems with trajectory tracking and reconfigurable formation for a multi-vehicle system expressed as a first-order system. Specifically, we describe a problem that cooperatively controlled vehicles keep geometric configuration among the multiple vehicles while the vehicles are moving in formation. In other words, each of the vehicles must change its position individually to keep the geometric configuration while the vehicle is moved by a cooperative control. In order to achieve this objective, we basically extend our previous result which was a control algorithm to surround a moving target by a group of vehicles cooperatively. The algorithm was based on a consensus algorithm which was cooperative control. In addition, we apply a leader-follower structure to our cooperative algorithm so that a leader can individually provide each of the followers with commands. Finally, the proposed approach is validated by some simulations.

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We propose a method for the optimal design of shock absorbers having magnetorheological fluid (MR). This method combines both parameter identification and optimization procedures. In the first step, the optimum orifice areas of a shock absorber are obtained by considering the minimum falling body mass. In the second step, the optimum electric current applied to the magnetorheological fluid in the shock absorber is obtained for a maximum falling body mass. Validation of this method is carried out by a comparison of the experimental results with simulation predictions. It is clarified that the optimum resisting forces obtained by the experiment are consistent with those of the simulation results, and the present method is effective for the optimal design of MR shock absorbers.

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This paper considers the time-optimal motion and obstacle avoidance trajectory generation for industrial robots. Although there are many previous works that had a similar objective, the generation of the trajectory for a general type of robot is still challenging because high computation time is required. This research focuses on a common type of robot that has a simple structure and moving environment. This limitation allows us to generate the trajectory in a much simpler and practical manner. In addition, oscillation suppression can be considered in the trajectory generation in the proposed approach. The real-time modification of the optimal trajectory is often required from a practical point of view. To avoid the recalculation of the trajectory that requires high computation time, we propose a real-time modification method of the trajectory. Simulation and experimental results demonstrate the effectiveness of the proposed methods.

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Bicycles are popular with the general public because of their low price and easy maintenance, and they will be an important vehicle in the future because of their low environmental load. Improving the comfort of the ride is one of the important factors that will lead to increased popularity. We attempted to increase comfort by reducing vibration, and evaluated the results with a subjective test. We determined that low frequency vibration of the seat greatly affected the comfort of the ride. We then performed a transfer path analysis (TPA) and a hammering test to investigate how the vibration characteristics of the bicycle affected the vibration of the seat. Through TPA, the rear of the bicycle frame was found to have a high influence on the seat vibration, and the vibration behavior was obtained by modal analysis. In order to reduce seat vibration, a spring was inserted in the front of the seat and, to increase the stiffness, a steel plate and bolts were attached to the rear of the frame. As a result, the seat vibration while riding was decreased by about 10 dB, and the comfort of the ride was greatly improved.

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Only10-16% of the fuel energy is used to drive the car-to overcome the resistance from road friction and air drag. One important loss is the dissipation of vibration energy by shock absorber of the vehicle suspension due to road irregularity, vehicle acceleration and deceleration. A prototype of regenerative shock absorber (RSA)was developed and its performance was studied.The prototype of RSA mainly consists of a gear transmission system, one way bearing and an electromagnetic generator.The RSA's damping coefficient, its capacity to absorb energy and its ability to regenerate electrical energy were measured for various input frequencies, amplitudes and electrical loads. A quarter car model which consists of the developed RSA,a mass anda spring with specific damping ratio of ζ=0.6 and ζ=0.8 was tested. The test was done using a quarter car suspension test rig to investigate the performance of suspension which uses RSA and the generated electrical energy from RSA. The results are reported and discussed in this article.

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