Advanced Materials Research Online: 2013-01-25 ISSN: 1662-8985, Vols. 655-657, pp 1175-1178 doi:10.4028/www.scientific.net/amr.655-657.1175 2013 Trans Tech Publications, Switzerland The operating principle and experimental verification of the hydraulic electromagnetic energy-regenerative shock absorber Chengcai Zhang a, Zhe Xiong b, Zhigang Fang c, Xuexun Guo d School of Automotive Engineering, Wuhan University of Technology, Wuhan, 430070, China a zhangchc@163.com, b xiongzhechina@yahoo.com.cn, c zuoleng136@163.com, d guo6531@163.com Keywords: HESA, energy-regenerative, shock absorber, generator, motor Abstract. This paper introduces a new type of shock absorber: hydraulic electromagnetic energy-regenerative shock absorber (HESA), which can simultaneously implement the function of damping vibration and regenerating a portion of dissipated energies generated from passing through the damping hole. A test bench was trial-produced and used to prove the feasibility of the energy-regenerative scheme. The situation that hydraulic motor rotational speed has a sudden change in the energy regenerating process is theoretically analyzed. Introduction The hydraulic electromagnetic energy-regenerative shock absorber is a new designed shock absorber. The research on energy-regenerative shock absorber was begun in 1990s. Nissan proposed a kind of hydraulic active suspension based on hydraulic pump[1]. The suspension utilizes the vibration energy to dampen the vibration and achieves a better ride comfort by regulating its system pressure. In the following years, the energy-regenerative shock absorber based on linear motor had developed rapidly[2,3]. In 1995, Okada proposed an electromagnet energy-regenerative system which used linear motors to regenerate the energy[2]. However, this idea had a disadvantage that the shock absorber had a dead band, means that the shock absorber is unable to provide enough damping force when operating on a relative low speed. In 1998, Suda proposed a hybrid suspension. Two linear motors were added on a passive suspension, one of which was used to regenerate energy, the other was used to active control the suspension[3]. However, from experiments Gupta found that the efficiency of linear motor was much lower than the rotary motor s, and the cost of linear motor was also relatively high, which of these restrained the development of energy-regenerative shock absorber based on linear motor[4]. In 2000, Suda adopted an new method which connected a ball screw to a rotary motor to regenerate the energy of shock absorber, and proved the feasibility of that design by conducting simplified experiments[5]. Zuo lei designed a energy-regenerative shock absorber by combining the pinion and rack and rotary motor, and proved its feasibility by conducting a mount of simulations and experiments[6]. Xu Lin proposed a hydraulic electromagnetic energy-regenerative shock absorber by combining the hydraulic transmission and rotary motor, and did lots of corresponding simulations and experiments[7]. Operating principle of HESA The operating principle of HESA is shown in Fig. 1. It is composed of a hydraulic cylinder, a hydraulic rectifier, accumulators, a hydraulic motor, a generator, and pipelines and so on. Hydraulic cylinder under external excitation begins to do back and force movement, forcing the high pressure oil out of hydraulic cylinder into the hydraulic rectifier which consists of four check valves. After being rectified by hydraulic rectifier, the high pressure oil flows out in a single direction. An accumulator is used to steady the oil flow so that the oil flow is able to drive the hydraulic motor smoothly, then the generator rigidly connected to hydraulic motor can be driven accordingly. The oil flow passed through the hydraulic motor continues to work. A Low pressure accumulator is located on the way where oil flow back to shock absorber. The operating principle of low pressure accumulator is similar to gas chamber of twin-tube damp s All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, www.ttp.net. (ID: 130.203.136.75, Pennsylvania State University, University Park, USA-10/05/16,16:59:19)
1176 Engineering Solutions for Manufacturing Processes Prototype and Test bench Fig. 1 Schematic diagram of HESA According to the hydraulic schematic diagram shown in Fig.1, Fig.2 shows the trial-produced principle prototype of HESA and the built relevant test bench in accordance with QC/T 545-1999 standard. The hydraulic cylinder, accumulator2 and hydraulic rectifier are integrated into the principle prototype of HESA. Before starting the test, it must be ensured that there is no air in the oil circuit. Otherwise, it would result in distortion of measured damping force as well as the abnormal rotational speed of hydraulic motor. During the test, it must also be ensured that each line, component and mechanism are perfectly sealed and completely leak free. Otherwise, the damping force and rotational speed of hydraulic motor would be gradually decreased. The test data would be considered invalid when above two circumstances occurred. Tests Fig. 2 Prototype and Test bench The prototype HESA was tested on test bench in accordance with QC/T 545-1999. Excitation frequency is set to 1.67Hz; excitation mode is displacement input which is a sinusoidal excitation of amplitude of 50mm. The generator is connected to an electronic load which monitors the generated voltage and power based on different currents (Fig. 3). Fig. 4 shows the hydraulic motor rotational speed to same time abscissa in Fig. 3. The current load is set by constant-current control. At the initial time the current is set to 0, the generated voltage and power are about 65V and 0. The hydraulic motor
Advanced Materials Research Vols. 655-657 1177 rotational speed is about 2820rev/min. Then orderly set the current to 5A, 10A and 20A. The generated corresponding voltages, powers and hydraulic motor rotational speeds are shown in Table 1. Fig. 4 shows that due to the effect of accumulator1, the rotational speed of motor changed suddenly once adjusting the current. To give a detail explanation, firstly analyzes the energy transfer equation of hydraulic motor and generator. The rotational speed and the torque of operating hydraulic motor meet the following Eq. 1: Q n= ηv q Pq e T = η m 2π (1) Where n is the rotational speed of motor; Q is the flow of motor; q is the motor displacement; η v is the volumetric efficiency of motor; η m is the mechanical efficiency of motor; T is the output torque of motor; Pe is the differential pressure between import and export of motor. The generator drove by hydraulic motor meets the following Eq. 2: Ve = kvw T = J θ + kti (2) Where V e is the eletromotive force of generator; k v is the back-emf constant of generator; w is the rotor speed of generator; T is the input torque of generator; J is the moment of inertia of rotor; θ is the rotary acceleration of rotor; k t is the torque constant of generator; I is the current. 5A 10A 20A Fig. 3 Voltage and power at different current Fig. 4 Rotational speed of the motor Table 1 The stable motor speed and the damping force at different current value Current (A) Rotational speed (rev/min) Voltage (V) Power (W) 0 2820 65 0 5 2510 48 240 10 2260 40 400 20 1900 27.5 550 From Eq. 2, the sudden increase of current I leads to a sudden increase of input torque of generator T as well as output torque of hydraulic motor. In Eq. 1, the differential pressure Pe between import and export of motor increases accordingly. Since the pressure in export always changes a little, means the pressure in import should have a sudden change. The accumulator1 pushed up by a higher pressure in the import is opening larger and able to store more oil. In this case, the volume of oil worked on
1178 Engineering Solutions for Manufacturing Processes hydraulic motor decreases rapidly. Consequently, the hydraulic motor rotational speed is suddenly decreased. After a while when the current is stable at 5A, the accumulator reaches its equilibrium position. Even though there exists a little fluctuation, the net intake or net discharge volume of oil is 0, therefore the rotational speed also reaches its equilibrium position. Similarly, the above analysis based on Eq. 1 and Eq. 2 as well as the characteristics of accumulator can be used to explain the sudden increases of hydraulic motor rotational speed, so this situation won t be cover again here. Fig. 3 and Table 1 both show the achieved maximum power 550W under the experimental sinusoidal excitation at a peak-to-peak amplitude of 50mm, frequency of 1.67Hz and controlled current of 20A. Even though the current is set to 5A, the achieved power transmitted to electronic load can be as high as 240W. All these test data proved the feasibility of energy-regenerative scheme of HESA. Conclusions This paper firstly illustrates the energy-regenerative principle of HESA. A principle prototype of HESA was trial-produced and a relevant test-bed in accordance with QC/T 545-1999 standard was built. The experiment on principle prototype of HESA has proved the feasibility of energy-regenerative program. By controlling the current in load circuit, the energy regenerated is able to be limited in a certain range. Based on the operating principles of hydraulic motor and generator, the sudden change of rotational speed of hydraulic motor was explained. Acknowledgements The authors gratefully acknowledge the National Natural Science Foundation of China by 2011(Project No. 51075312) and Wanxiang Group Corporation Technology Center. References [1] Aoyama Y, Kawabate K, Hasegawa S. Development of the fully active suspension by Nissan. SAE Paper :901747 [2] Okada Y, Harada H. Active and regenerative control of electrodynamic vibration damper [C]. Proceedings of the 1995 Design Engineering Technical Conference, USA: ASME, 1995: 595-602 [3] Suda Y, Nakadai S, Nakano K. Study on the Self-Powered Active Vibration Control. Transactions of the Japan Society of Mechanical Engineers, 1998, 64(628): 4770-4776 [4] Gupta, A., Jendrzejczyk, A. J., Mulcahy, M. T. and Hull, R. J. Design of Electromagnetic Shock Absorbers [J]. International Journal of Mechanics and Materials in Design, 2006, 3(3): 285-291 [5] Suda Y., Suematsu K., Nakano K., et al. Study on electromagnetic suspension for automobiles-simulation and experiments of performance[c]// Proceedings of the 5th International Symposium on Advanced Vehicle Control, Ann Arbor, Michigan, USA: 2000: 699-704 [6] Zhongjie Li, Zachary Brindak, and Lei Zuo. Modeling of an Electromagnetic Vibration Energy Harvester with Motion Magnification. Proceedings of the ASME 2011 International Mechanical Engineering Congress & Exposition, IMECE2011, Denver, Colorado, USA, November 11-17 [7] Xu Lin. Structure Designs and Evaluation of Performance Simulation of Hydraulic Transmission Electromagnetic Energy-regenerative Active Suspension[C]//Society of Automotive Engineers. SAE 2011 World Congress & Exhibition. Michigan: SAE, 2011: 2011-01-0760
Engineering Solutions for Manufacturing Processes 10.4028/www.scientific.net/AMR.655-657 The Operating Principle and Experimental Verification of the Hydraulic Electromagnetic Energy- Regenerative Shock Absorber 10.4028/www.scientific.net/AMR.655-657.1175 DOI References [3] Suda Y, Nakadai S, Nakano K. Study on the Self-Powered Active Vibration Control. Transactions of the Japan Society of Mechanical Engineers, 1998, 64(628): 4770-4776. 10.1299/kikaic.64.4770 [4] Gupta, A., Jendrzejczyk, A. J., Mulcahy, M. T. and Hull, R. J. Design of Electromagnetic Shock Absorbers [J]. International Journal of Mechanics and Materials in Design, 2006, 3(3): 285-291. 10.1007/s10999-007-9031-5