ARTC provides the techniques of developing Electric Power Steering (EPS) module for electric buses. The module integrates the torque and angle sensor, bevel gears, reduction gears, and the electric motor, which can be combined with the steering system of the electric bus. Based on the torque sensor signal, the electronic control unit (ECU) calculates the required assistance torque and controls the assist motor to drive the steering shaft. While driving the electric bus, the electro-hydraulic power steering system can be shut down and the steering assistance can be provided by EPS module on the driver’s demand. As a result, the energy efficiency of the electric bus can be improved effectively. After actual vehicle test, the EPS module saves 91% of the electrical energy consumption compared with the existing EHPS system under the single turning operation scenario. Higher energy-saving benefits can be achieved based on the actual driving route.

1.Rated voltage: 24V
2.Rated current: 20A
3.Control frequency: 20kHz
4.Sinusoidal commutation: Field oriented , space vector pulse-width-modulation control
5.Module max output: 120 Nm
6.Control Logic: Basic assistance, EPS and EHPS integration control

The EPS module can be used in electric vehicles (EV), hybrid vehicles (HEV), internal combustion engine vehicles (ICE) and other automobiles which use recirculating ball steering mechanisms (with pitman arm).

The EPS module can provide steering assistance on the driver’s demand which has energy-saving benefits. In addition, the EPS module has active return and stability compensation functions. Therefore, the EPS module can be integrated with the lane departure warning system to achieve lane keeping assist. ARTC has established EPS technologies which include mechanical module design, system integration, system control logic design, etc. The establishment can make domestic component manufacturers have capabilities of system integration and opportunities of getting into the electric bus steering system supply chain to meet future trend of active safety.