DSP-based electric power assis

Abstract. This paper introduces a design and implementation of electrically
assisted power steering (EAS) using BLDC motor for a vehicle. The control archi-
tecture consists of two layers of control, namely the vehicle speed associated control
and the torque assist control. In the higher level of control architecture, the vehicle
speed controller works as an assistance level controller for the steering effort. In
the lower level, the torque controller gives the effort level control. This has been
realized by torque sensor and vehicle sensor interfaced in the DSP. For implement-
ing in the system, a DSP-based BLDC motor controller with three-phase inverter
module is specially designed using Hall-effect sensor feedback and a single dc-link
current sensor. This work is implemented in a Light Commercial Vehicle having
a recirculating ball type gear. This is for the first time (EAS) being implemented
for this type of vehicle any where in the world. Generally, EAS having clutch to
disconnect the motor in high speed or abnormal conditions from the gear box. In
this implementation the motor is directly coupled to gearbox without clutch and all
abnormalities are handled by the processor. This is implemented without modify-
ing the vehicle supply system like changing the existing alternator or rating of the
battery and using the existing sensors. The design is such a way that the feel of the
driver assistance can be varied easily at any time. The performance of the control
system is experimentally verified and it is tested in one of the Light Commercial
Vehicle (LCV).