140 Energy Regenerative and Active Control of Electro-Dynamic Vibration Damper

8/14/2019 140 Energy Regenerative and Active Control of Electro-Dynamic Vibration Damper

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ENERGY REGENERATIVE AND ACTIVECONTROL OF ELECTRO-DYNAMICVIBRATION DAMPER

Yohji Okada and Keisuke Ozawa Department of Mec anica Engineering, I ara i University, Japan

[email protected]

stract: Active vibration control is introduced to an electro-dynamic regenerative vibra-tion damper. It is intended to improve vibration reduction capability using theregenerated energy. This idea is applied to a moving mass type vibration ab-sorber and vibration control is performed. In the case of energy regenerativeontrol, a PWM step-up chopper is used to solve the dead zone problem. Act-

ive control signal is also produced by the other PWM chopper from the powersupply. However, energy regenerative and active control mode can not operateat the same time. A new control law is introduced to switch control mode and to

ollow the ideal force. The ideal force is calculated using the LQ control theory.Experimental setup is made to conrm the proposed technique and the dampingapability is tested.

ey words: regenerative damper, active control, dynamic absorber, digital control.

INTRODUCTION

Vibration control has been widely investigated and reported. Recently active

ibration control has been gradually used because of its high damping capab-lity such as high building, automobile suspension, and large space structures(Garcia et al., 1995; Alleyne and Hedrick, 1995). But there exist several dif-culties such as high power consumption and complexity of the system eventhough it has strong ability of vibration reduction. On the contrary, vibrationis a kind of energy and the actuator is a kind of energy converter, the vibrationenergy can be regenerated to electric energy. This idea of utilizing the vibra-tion energy and regenerating it to electric energy can lead to high cost savingand efciency (Okada and Harada, 1995).

In a previous paper, one of the authors reported the energy regenerativedamper using pulse width modulated (PWM) step-up chopper control (Kimand Okada, 2002a). By using the step-up chopper, electric energy can be regen-

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H. Ulbrich and W. Gnthner (eds), IUTAM Symposium on Vibration Control of Nonlinear Mechanisms and Structures, 233242 . 2005 Springer. Printe in t e Net er an s.


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Y. Okada and K. Ozawa

Figure 1. odel of the moving mass type damper system.

erated from the low voltage source to high battery voltage. Hence the dampercan regenerate even though the actuator velocity is in the dead zone region.The damping characteristics can be adjusted by changing the PWM duty ratio.

In this paper, active vibration control is introduced to an electro-dynamicregenerative vibration damper. It is intended to improve vibration reductioncapability using the regenerated energy. An electro-dynamic actuator is used asan energy regenerative damper and active control actuator. This idea is appliedto a moving mass type vibration absorber and vibration control is performed.In the case of energy regenerative control, a PWM step-up chopper is used tosolve the dead zone problem. Active control signal is also produced by theother PWM chopper from the power supply. However, energy regenerativeand active control mode can not operate at the same time. A new control lawis introduced to switch control mode and to follow the ideal force. The idealforce is calculated using the LQ control theory. Experimental setup is made toconrm the proposed technique and the damping capability is tested.

1. MOVING MASS DAMPER

In this paper the proposed active and regenerative damper is applied to a mov-ing mass type vibration damper.

1.1 Modeling of the System

The physical model of the system is shown in Figure 1. The external force isapplied to the main mass M , and the damping force f is applied between the

main mass and the damper mass . Then the equations of motion are writtenas follows, where the parameters used in the experiment are shown in Table 1.

+ x + + k(x d m x f + k(x x) 0 (1)

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Energy Regenerative and Active Control of Electro-Dynamic Vibration Damper

Ta e 1. Parameters of experimental setup.

Description Symbol ValuePrimary mass M 4.85 [kg]Primary spring constant 19809 [N/m]Primary resonant frequency n 63.9 [rad/s]Secondary mass 0.8468 [kg]Secondary spring constant 2510.5 [N/m]Mass ratio 0.1746Actuator constant 25 [N/A=Vs/m]

1.2 Damping ActuatorLinear voice coil motor (VCM) is used in this research for the damping actu-ator. Assuming the actuator is an ideal one, it has the following energy conver-sion property (Okada and Harada, 1995),

f i, e = v (2)

where f and v are the actuator force and velocity, and are the driving

voltage and the current, and is the actuator constant, respectively.

2. ACTIVE AND ENERGY REGENERATIVECONTROL

Single actuator is used as active and regenerative damper. Hence a new controlalgor thm s ntro uce to sw tch the control mo e etween the act ve anegenerative one to follow the ideal damping force.

2.1 Ideal Damping Force

The ideal damping force s calculated using the LQ control theory. Theerformance index is written as

=

[ x Qx + 2 ] t (3)

where the state variable x s composed of the main and submass displacementsand their velocities, and Q [ m2] and [W N 2] are the weights for them.

Solving the Riccati equation we have the following ideal damping force.

f = K x x x x (4)

The displacements of the main and sub masses are measured by the laser dis-lacement sensors and the velocities are calculated from the observers.

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Figure 2. PWM step-up chopper circuit. Figure 3. Damping characteristics of PWM step-up chopper.

Figure 4. Schematic of control system.

2.2 PWM Stepup Chopper Regenerative Damper

The energy regenerative damper is shown in Figure 2. Without stepup chopper,which is shown in the dashed block, the damper has the undesirable dead-zoneas shown by the dotted line in Figure 3.

eF b v F b (5)

In this region damping force becomes zero and energy is not regenerated. Thisis improved by introducing the PWM stepup chopper as shown by the solidline in Figure 3 (Kim and Okada, 2002a).

2.3 Incorporating Active Control

The regenerative force is used when the regenerative circuit can control theactuator force close to the ideal force, while the active control is introduced inthe other region. For this purpose new control circuit is introduced as shown

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Figure 5. Energy regenerative mode I. Figure 6. Energy regenerative mode II.

Figure 7. Active control mode I. Figure 8. Active control mode II.

in Figure 4. The left side voice coil motor (VCM) is used to excite the main

structure, and the bigger VCM is installed between the main mass and theauxiliary mass as the damping actuator. The control is switched as shownin Figures 58. All the control modes are controlled with the pulse widthmodulated (PWM) signals using the analog switches (MAX4601).

The control modes are switched whether the regenerative control is possibleor not as:

2

R2 0: Energy Regenerative Mode

2) Other cases: ctive Control ModeIn case 1), the ideal force and the actuator velocity is out of phase, then

the brake force (regenerative force) can produce damping force. According tothe velocity direction the actuator current ows as shown in Figure 5 or as inFigure 6. In this case the active control switches 1 and 2 are turned OFF, and

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Figure 9. Schematic of experimental setup.

the regenerat ve current s controlle only y the sw tch as

| f | | f | WM of switch S high| f | | f | WM of switch S low

In case 2), the damping force should be produced with the active control.The actuator is controlled as shown in Figure 7 or as in Figure 8 according tothe control force direction. Notice that the regenerative switch should alwaysbe OFF and the active control switches are controlled as

0 , PWM o 1 gh, wh le 2 OFFf 0 , f f PWM of 1 ow, while 2 OFFf 0 , f f PWM of S 2 igh, while S 1 OFF

f 0 , f f PWM of S 2 ow, while S 1 OFF

Even all the switches are OFF, the regenerative current will ow when theactuator speed is very high and regenerative voltage is over the battery voltagebecause the actuator is always connected to the battery through the diodes.

3. EXPERIMENTS

To conrm the proposed active and regenerative control, the experimental

setup is made as shown in Figure 9.

3.1 Experimental Setup

The experimental setup and control system are shown in Figures 9 and 4. Thetwo masses are supported with two linear guides horizontally. The damping

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Ta e 2. Experimental conditions.

Power supply [V] 2.4, 6.0, 10.0Disturbance [N] 1, 5, 10Switch PWM driving

Figure 10. Frequency response: Bat. =2.4 [V].

Figure 11. requency response: Bat. =6.0 [V].

actor of the main structure is about = 0.1 ( = 62 [Ns/m]). In the left of Figure 9 the auxiliary mass m s connected to the main mass with the springof . In the middle a strong actuator is installed; the moving coil is connectedto the auxiliary mass and the massive PM part is used as the main mass. Theyare controlled by a DSP (dSPACE DS-1103). The sinusoidal signal from DSPs added to the disturbance voice coil motor through a power amplier. Theelocity of the damping actuator is measured by the current which ows amall resistance R 0. . The displacements of main mass and the auxiliary

mass d are measured by the laser displacement sensors (KEYENCE LB-60). They are put into the DSP through A/D converters. The state feedback signal is calculated in the DSP and the PWM signals from the DSP controlthree switches , 1 an S 2.

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Figure 12. Frequency response: Bat. =10 [V].

Figure 13. Consumed and regeneratedpower.

3.2 Results

According to the previous energy regenerative and active control the exper-iment is performed. The weights for the performance index are determinedas

Q =

0 0 00 0.01 0 0

0 0 0 00 0 0 0

[ m2], = 0 [ N 2] (6)

Frequency Response. The frequency responses are measured and the res-ults are shown n F gures 1012. The responses are compare w th the casecontrolled by the ideal linear damping force . The experimental conditionsare shown in Table 2.

A single resonant peak is recognized with the higher disturbance force inFigure 10. This is considered due to the small maximum active force whichis not enough for reducing the peak. Increasing the supply voltage to 10 [V]relatively good damping is recognized as shown in Figure 12.

Consumed power and regenerated power are compared in the case of supplyvoltage 10 [V], as shown in Figure 13. This is the results of the frequencyresponse case shown in Figure 12.

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Figure 14. Random excitation (No con-rol).

Figure 15. Random excitation (Withcontrol).

In all frequency range the power is consumed for active control, while theower is regenerated within the narrow region near resonant peak. This in-cates that near the resonant requency the system can regenerate v rat on

ower. However the active consumed power is much bigger in the other re-gion. This response conrmed that the proposed system can regenerate the

ibration power even it is restricted within the narrow frequency region near

the resonance an also the act ve control s operate at the same t me.

Response of Random Excitation. A random force excitation is tested andecorded. The mean value of random force is 5 [N], and the supply voltage is 10

[V]. Ran om s gnal s suppl e rom FFT analyzer (MTS S gLa Vers on3.2.4)with the frequency band of 10 [Hz]. The excited displacement and the powerare compared with and without control as shown in Figures 14 and 15. The

ower response is shown in the bottom of Figure 15, where the positive signals the consumed power due to the active control while the negative one is theegenerated power.

Comparing the displacement time responses in the middle of Figure 15 withthe bottom one in Figure 14, the amplitude is reduced about 1/4 with the pro-

osed control. However the regenerated power is very small and the main isthe consumed power by active control as indicated in the bottom of Figure 15.

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This might be improved by improving the control circuit using the hardwarePWM modulation circuit.

4. SUMMARY

In this paper active control is incorporated to the PWM setup chopper energyregenerative damper. The part of active control energy can be supplied fromthe regenerated energy. Also regenerative control is planned to reduce the vi-bration energy. From the experimental results the proposed idea is partly suc-ceeded, but the vibration reduction and the regenerated energy is not enough.This is considered due to the slow PWM duty ratio change using the softwarechange in dSPACE. Further work is continuing to use the hardware PWM mod-ulation circuit to improve the system performance.

REFERENCESAlleyne, A. and Hedrick, J.K. (1995). Nonlinear Adaptive Control of Active Suspensions. IEEE

Trans. on Control Systems Technology , Vol. 3, No. 1, pp. 94101.Garcia, E., Webb, C.S. and Duke, M.J. (1995). Passive and Active Control of a Complex Flex-

ible Structure Using Reaction Mass Actuators. ASME Trans. on Vi ration an Acoustics ,Vol. 117, No. 1, 116122.

Kim, S.-S. and Okada, Y. (2002a). Variable Resistance Type Energy Regenerative Damper Us-ing Pulse Width Modulated Step-up Chopper. ASME Trans. on Vi ration an Acoustics ,Vol. 124, No. 1, pp. 110115.

Kim, S.-S. and Okada, Y. (2002b). Variable Resistance Type Energy Regenerative Suspension. JSME Trans. , Series C, Vol. 68, No. 675, pp. 32243229 [in Japanese].

Kim, S.-S., Yonemura, J. and Okada, Y. (1997). Regenerative Suspension System with an Op-timally Tuned Resonant Circuit. In Asia-Pacic Vi ration Contro 97 , pp. 11411146.

Okada, Y. and Harada, H. (1995). Active and Regenerative Control of Electrodynamic VibrationDamper. In Proc. of the 1995 Design Engineering Technical Conf. , Vol. 3, Part C, ASMEDE-Vol. 84-3, pp. 595602.

Okada, Y. and Harada, H. (1996). Regenerative Control of Active Vibration Damper and Sus-pension System. In Proc. of the 35th IEEE Conf. on Decision and Control , pp. 47154720.

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140 Energy Regenerative and Active Control of Electro-Dynamic Vibration Damper