The "E-Jet” concept vehicle sponsored by Hans Hermann Voss-Stiftung innovates steering by providing an innovative actuator for a steer-by-wire system. Without a physical connection to the wheels in place, no mechanical feedback of the forces and moments associated with the tire-road contact can be gained. This feedback helps the driver stabilize the vehicle. In order to ensure the driver's interaction with the vehicle, the steering bow was developed as an active actuator, which means that the steering bow movement can be influenced by an electromechanical actuator, which enables the steering bow to provide feedback on the vehicle’s driving dynamics.
Use of HBM’s Multi-Component Transducers in the Steering Bow
Only the tangential component of the actuating force is relevant for actuating the steering bow. Nevertheless, the use of a multi-axial force sensor is required in the current phase of development in order to detect, analyze, and compensate for the influence of deviation forces and moments. In addition, it is essential that the measuring system is not only reliable but also capable of accurately recording the user’s force input. With an accuracy class of 0.2 and a compensation matrix for reducing crosstalk effects, HBM's 6-axial MCS10-005-6C multi-component transducer fulfills these requirements.
The Importance of Precise Measuring Instruments in the Steering Lever
The steering bow is designed as an active actuator with force input and displacement feedback. The driver receives feedback concerning the vehicle’s driving dynamics via the position change detected by the steering bow. This results in the subdivision of the steer-by-wire system’s control concept into two phases: setpoint setting and feedback synthesis.
The force exerted by the driver on the handle element is measured using the multi-axial force sensor. Strain gauges allow for the measurement of forces and moments in the force sensor. These are then amplified, digitized, and evaluated in the real-time computer. Based on the sum of the forces on the left- and right-hand sides (with the sign of the force on the right-hand side being inverted since both sensors give a positive signal for the same direction of actuation), setpoints for the steering angles of the front wheels are calculated as a function of the vehicle speed and the vehicle geometry. In the "E-Jet" concept vehicle, these steering angle setpoints are implemented by steering motors.
The steering motors output the actually implemented steering angle that depends on the driving situation and the road conditions. Based on the actual steering angles of the wheels and the driving conditions the real-time computer calculates a setpoint for the steering-bow angle. This is implemented by the actuator at the steering bow.
The "E-Jet" project developed an ultra-light vehicle with a serial bio-hybrid drive in the form of a combination of electric and pedal drive. The steering lever, also known as the steering bow, specially designed for this project, offers a new driving experience. A reliable measuring system had to be developed to ensure precise input of the driver's force and thus the exact transmission of the steering movement to the vehicle.
With the MCS10-005-6C, HBM has introduced a multi-component transducer that enables both the measurement and analysis as well as the compensation and reduction of the given deviation forces.
The project resulted in the development of the steering bow. The multi-component sensor enables the precise transmission of steering movements. In combination with the calculation of the setpoints for the steering angle, the "E-Jet" becomes steerable and drivable.
Rheinisch-Westfälische Technische Hochschule Aachen (RWTH Aachen University) is the largest technical university in Germany with more than 45,000 students. With the ika, the" Institute for Motor Vehicles", the university has at its disposal an innovative testing facility for motor vehicles. The institute is running research, among other things, on "Vehicle Intelligence & Automated Driving", "Vehicle Concepts & HMI", and "Energy Management & Drives". In addition to the training of future car manufacturers, the ika aims to innovate the modern transport system, for instance, with the „E-Jet" project.
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