Hitachi Exhibits Electromagnetic Suspension System

Oct 30, 2006
Keisuke Ogawa, Nikkei Automotive Technology
The electromagnetic suspension system
The electromagnetic suspension system
[Click to enlarge image]
The electromagnetic suspension system (excluding the sensors) is described below. When the sensor detects an impact while the vehicle is moving, the power cable generates a magnetic field in the linear motor to adequately control the movement of hydraulic damper.
The electromagnetic suspension system (excluding the sensors) is described below. When the sensor detects an impact while the vehicle is moving, the power cable generates a magnetic field in the linear motor to adequately control the movement of hydraulic damper.
[Click to enlarge image]
The graph in which compared to the case of hydraulic damper alone shows the system reduces vibration around the frequency of 1.5 Hz by approx. 8 dB.
The graph in which compared to the case of hydraulic damper alone shows the system reduces vibration around the frequency of 1.5 Hz by approx. 8 dB.
[Click to enlarge image]

Hitachi, Ltd. exhibited its electromagnetic suspension system under development at the EVS-22 electric vehicle exhibition.

It is an active suspension system composed of an acceleration sensor, a cylindrical linear motor, a hydraulic damper and a spring. The combination of hydraulic damper and linear motor allows faster response than that of a system using only a hydraulic damper, thereby achieving greater comfort.

The system uses the acceleration sensor for vertical direction and a suspension stroke sensor to detect input from the road surface. The linear motor in the system is controlled in response to the input to reduce the vibration of vehicle in the vertical direction.

Compared to the previous hydraulic active suspension systems, the time required to suppress vibration after the detection of input is reduced. In addition, the new system eliminates the need of a hydraulic pump because it is controlled by the linear motor. The target application is large SUVs. The timeline for commercial launch is yet to be decided.

Meanwhile, Bose Corp. has also developed an electromagnetic suspension system. Bose's system differs from Hitachi's in that it is designed so that a linear motor substitutes for a spring and damper while Hitachi's uses a coil spring and a hydraulic damper in combination with the linear motor.