A new system has been developed for measuring the driving- and braking-torques acting on passenger car wheels. The RWT (Rotating Wheel Torquemeter) is intended above all for vehicle dynamics applications, particularly the development of control systems for dynamic stability, traction control and ABS, as well as investigations of brake fade, brake judder, measurement of transmitted power and determination of friction values, coast down characteristics, and safety tests.
The modular system consists of three main components: The torque sensor, the transceiver head for telemetric signal transmission and the control unit located in the vehicle. The torque-sensing device can be fitted to the vehicle with the aid of hub and rim adapters. This allows rapid installation to different vehicles. The torque measurement is achieved via piezoelectric quartz force sensors. In addition to the torque signal, there is provision on the rotating element of the My sensor for installing four K-type thermocouple elements, e.g. for monitoring temperatures on the brake disk.
The measured data are sent from the transceiver head by telemetric signal transmission to the control unit in the vehicle. The transceiver head includes all components for the data acquisition, telemetry and telecommand. The power is supplied by batteries.
The control unit consists of a 32-bit processor and digital-, serial-, CAN- and analogue interfaces. Radio frequency links, based on a DECT transceiver module, as used in cordless phones, are set up between the control unit and the transceiver heads attached to the system. One control unit can serve up to four transceiver heads.
User access for commands and measured data is possible through CAN and RS232 interface. Analogue data output is also available.
The layout of the measuring system, technical data and examples of typical measurements are presented.