Study on the Self-powered Active Vibration Control

A method of active vibration control using regenerated vibration energy, i.e., the self-powered active vibration control is proposed. In this system, vibration energy is regenerated with an electric generator ,which is called energy regenerative damper, and is stored in a condenser. An actuator attains active vibration control using the energy stored in the condenser. A variable resistance is used to control output force of the actuator. Since the damping coefficient of the energy regenerative damper is uncertain when it regenerates vibration energy, it is required for the controller to be robust to parameter uncertainty; H∞ control method is applied to the system. Through experiments, the self-powered active control system is proved to have better isolation performance in comparison with that of a semi-active or a passive control system. INTRODUCTION Active vibration control has been applied to several systems. It has better isolation performance than a passive control system. However, an actuator requires external energy in the active control system. This is one of the drawbacks of an active vibration control system. In order to solve the problem of the energy consumption, a semi-active control system has been studied[1] and applied to practical systems[2]. In the semi-active control system, the variable damper whose damping coefficient can be changed, is controlled to produce force equal to the actuator would. Controlling the variable damper requires no energy. However, there is the limitation to produce the desirable force by controlling the damping coefficient of the variable damper; negative damping force cannot be produced. An active vibration control using regenerated vibration energy, i.e., self-powered active vibration control has been proposed[3]. In the self-powered control system, all the energy for active control is supplied from the damper which regenerates vibration energy. The system can realize active control without external energy and has better isolation performance than a passive or a semi-active control system. In this paper, the selfpowered active control is applied to a two-degrees-offreedom suspension system. The electric generator, which is called energy regenerative damper, is placed in the primary suspension. The energy regenerative damper absorbs the vibration energy and stores it in the condenser. An actuator is located in the secondary suspension. It attains active vibration control with the energy stored in the condenser. Output force of the actuator is controlled by the variable resistance. In the self-powered active control system, the energy regenerative damper reduces its damping force when it regenerates vibration energy[4]. H∞ control theory, which is robust to parameter uncertainty, is applied to the system. Through experiments, the self-powered active vibration control is realized and is proved to have better isolation performance than a passive or a semi-active control system. PROPOSED SYSTEM Figure 1 shows the proposed self-powered active vibration control system. Two linear DC motors are installed in the system. The linear DC motor in the primary suspension regenerates vibration energy and stores it in the condenser, and the linear DC motor in the secondary suspension uses the energy stored in the condenser to attain active control. The objective of the active control is to isolate the second mass m2 from disturbance. A variable resistance is used to control the armature current of the actuator. The linear motor in the primary suspension is called the energy regenerative damper and the linear motor in the secondary suspension is called the actuator. FIGURE 1: Self-Powered Active Vibration Control System ENERGY REGENERATION Circuit of the Energy Regenerative Damper Electric circuit of the energy regenerative damper is shown in figure 2. By relay switches, induced voltage is rectified, and the terminal of the motor can be connected to a condenser or to a short-cut circuit. When the motor is connected to the condenser, vibration energy is regenerated, and when the motor is connected to the short-cut circuit, it works as an ordinary passive damper. FIGURE 2: Electric Circuit of the Energy Regenerative Damper Passive Damper Mode We assume that induced voltage of the energy regenerative damper is proportional to the stroke velocity, and output force is proportional to a current of the armature. When the stroke velocity of the energy regenerative damper is & z1 , and the current is i1, induced voltage v1 and output force f1 are written as, v z 1 1 1 = ⋅ φ & (1) f i 1 1 1 = ⋅ φ , (2) where φ1 is proportional constant called motor constant. When both electric terminals of the energy regenerative damper are connected to a short-cut circuit, the electric current is,