Laboratory Testbed

1
Haptic Interface for Automotive Steer-by-Wire
Systems
LEES
Alejandro D. Dominguez-Garcia, Prof. John G.
Kassakian Massachusetts Institute of Technology,
Laboratory for Electromagnetic and Electronic
Systems

• Laboratory Test-bed
• The main purpose of the laboratory test-bed is to
  provide a mean of generating the sensed
  parameters needed for control of the
  Steer-by-Wire system.
• To Simulate the aligning torques on the wheels
  through a complete model of the vehicle dynamics.

• The Hand-Wheel Angle-Torque Characteristic
• According to 1, in a mechanical steering
  system, the hand-wheel angle-torque (?h - Th)
  characteristic is clearly one of the most
  important items that influences the driving
  feeling.
• The ?h - Th characteristic is influenced by the
  vehicle velocity, the tire properties, the
  suspension parameters, and the road.
• In a steer-by-wire system, different steering
  feelings can be obtained by modifying the ?h - Th
  characteristic.

Abstract During the last few years, the
automotive industry has focused efforts on the
development of Steer-by-Wire Systems. Among the
advantages of such a system, the most important
are the enhancement of passive safety systems and
the introduction of lateral active safety
systems. One of the goals in the development of
steer by wire systems is to provide the driver
with tactile feedback from the road. The
importance of force feedback or road feeling
has been well understood in both the
tele-manipulator systems and the automotive
field. Force feedback is one of the most valuable
parameters in providing for the driver with
accurate control of the vehicle. In this context,
it is very important to provide a tunable
realistic steering feel that ensures a
comfortable driving feel.
Thf(?h , V, Tire, Suspension, Road)
1 Vehicle Velocity Influence
2 Tire Properties Influence

• Generic Description an Steer-by-Wire System
• No longer a mechanical connection between the
  driver and the steering system.
• Significant similarities with tele-manipulator
  systems.
• The control of both the steering wheel and
  steering system rely on a unique controller.

• At higher vehicle velocity (V), the gradient
  Th/?h increases.
• At higher vehicle velocity, the hysteresis width
  of the Hand-Wheel Torque for zero Hand-Wheel
  Angle becomes narrower.

• As the Cornering Stiffness (CS) of the tire
  increases, the gradient Th/?h increases.
• As the Cornering Stiffness, the hysteresis width
  of the Hand-Wheel Torque for zero Hand-Wheel
  Angle increases.

3 Suspension Geometry Influence
4 Road Influence
Partial View of the Laboratory Test-bed
Block Diagram of a Power Assisted Steering System
References 1 H. Shimomura, T. Haraguchi, Y.
Satoh, and R. Saitoh, Simulation analysis on the
influence of vehicle specifications upon steering
characteristics, International Journal of
Vehicle Design, vol. 12, no. 2, 1991.
Acknowledgments F. Luis Pagola, Professor of
Electronics and ControlUniversidad Pontificia
Comillas, Madrid, Spain. T. A. Keim, Principle
Research Engineer
Massachusetts
Institute of Technology, Cambridge,
Massachusetts. John F. Banzhaf


Northeastern University, Boston,
Massachusetts. This research has been fully
supported by the Sheila and Emanuel Landsman Fund

• As the Caster increases (Ca), the gradient Th/?h
  increases.
• As the Caster increases, the hysteresis width of
  the Hand-Wheel Torque for zero Hand-Wheel Angle
  decreases.

• As the Friction Coefficient (?) between the tire
  and the road increases, the gradient Th/?h
  decreases.
• As the Friction coefficient between the tire and
  the road increases, the hysteresis width of the
  Hand-Wheel Torque for zero Hand-Wheel Angle
  becomes narrower.

Block Diagram of an Automotive Steer-by-Wire
System