H∞ multi-objective implementation for energy control of electromagnetic suspension

In this paper, an electromagnetic shock absorber for passenger car has been designed, fabricated and tested. Multi objective H∞ Controller has been designed and implemented on quarter car test rig. Controllers have been designed to minimize sprung mass acceleration, power requirement and to maximize harvesting energy. Proportional-Integral (PI) Controller with currents input tracking reference has been also implemented for comparisons. Shock absorber has been designed and prototyped to harvest vibration energy and to be controlled by electric current. The shock absorber uses DC permanent magnet motor. Damping force and regenerated current of prototype have been tested on Auto Damping Test Machine (ADFT). The prototype is able to generate 2.59A maximum current with 183.3N damping force when 20 Ω external loads are applied. A DOF mass-spring-damper test rig has been constructed for controller implementation. Simulations have been conducted for verification. With optimal state feedback gain, K_opt = -514.11 -127.59 -0.00017 -1.14 -0.42 0 0.26], H∞ Multi objective controller is attaining RMS of body acceleration arms= 1.2m/s², maximum suspension stroke SWSmax= 0.016m, and average power consumption Pcons = 134 Watt. Root Mean Squared Error (RMSE) among experimental and simulations are: 0.31 m/s², 0.0058m and 2.91 A respectively for body acceleration, suspension travelling and supplied current. With PI controller parameter: K_p = 0.4 and K_i =0.5, feedback gain C_g = 2 and C_s= 0.3, RMS of body acceleration a_rms= 1.16m/s², maximum suspension stroke SWS_max = 0.03m, and average power consumption P_cons = 178 Watt. Root Mean Squared Error (RMSE) among experimental and simulations are: 0.85m/s², 0.0066m and 2.73 A respectively for body acceleration, suspension travelling and supplied current.