TECHNICAL SEMINAR ONHill-Start Assist & Downhill Assist

Presented by,Pratham Prakash

DEPARTMENT OF MECHANICAL ENGINEERING

ADICHUNCHANAGIRI INSTITUTE OF TECHNOLOGY

HILL-START ASSIST CONTROL &

DOWNHILL ASSIST CONTROL

INTRODUCTIONHill-Start Assist Control (HAC) is

the new mechatronic technology as a safety feature that detect the backward motion of the vehicle on hill or slope, that electronically controls and increases brake pressure at each wheel.

•Downhill Assist Control (DAC) automatically controls the brakes to maintain a constant low speed when descending slopes, helping reduce wheel lock and keeps good traction to maintain vehicle control.

Hill-Start Assist ControlThere may be unexpected cases for the driver

where the vehicles may slide when starting on sudden hills or slippery surfaces. HAC minimizes vehicle roll-back by controlling brake fluid pressure as the driver's foot is removed from the brake to the accelerator on such steep incline.

The HAC system is designed to help prevent the vehicle from rolling backward or slipping sideways during transition from a stopped position to climbing an upgrade.

The HAC system helps increase control on steep upgrades and prevents individual wheels from locking.

Without the HAC system, backward rolling or slippage occurs in steep inclines.

How it works……

• The HAC system determines the driver’s intended vehicle direction from the present gearshift position of the transmission, the moving direction of the vehicle wheels and the wheel speed of the four wheels through the use of active wheel sensors.

• An active wheel sensor is located in each wheel. The sensor uses a rotating magnetic encoder located in the wheel hub to detect a magnetic field.

• The active wheel sensor is then able to detect the rotating wheel direction.

• The active wheel sensors detect rotation direction. This allows the active wheel sensors to digitally process the signals and provide wheel direction information.

• When backward rolling or slippage occurs, the HAC system is automatically activated.

• Upon activation the HAC system gently applies the brakes. The system measures the necessary brake pressure of each wheel to help prevent individual wheels from locking and causing vehicle slippage.

• Without HAC, driver must quickly & precisely switch from the brake pedal to the accelerator pedal. With HAC however, the driver can start off easily & operate the pedal in a relaxed manner because HAC reduces the backward speed of the vehicle.

How!!!!!.....

Downhill Assist Control• When the vehicle is descending a steep hill &

engine brake alone cannot provide a sufficient deceleration force.

• DAC effects 4 wheel brake control to ,maintain a constant, low speed. Thus, the vehicle is able to descend in a stable manner without causing the wheels to become locked.

• When the vehicle descends a steep hill without DAC, driver must pay close attention to the brake & accelerator pedal. However with DAC, driver can concentrate on steering operation, without accelerator & brake pedals operation.

Without the DAC system, wheels lock when pressing the breaks in steep slopes.

The DAC system improves directional control during descent on steep or slippery surfaces.

How it works……The active wheel speed sensors and ECU (Engine

control unit) enable the operation of the DAC system by determining current road conditions & gradient of hill.

The skid control ECU computes the vehicle speed, travel direction, gradient of hill in accordance with signals from speed sensor and deceleration sensor and these effects, brake control to attain the target vehicle speed.

The DAC system will calculate the required brake hydraulic pressure for each wheel, allowing each individual wheel to meet the target vehicle speed.

If the accumulator pressure drops during this operation, the skid control ECU receives the signals from pressure switch and actuates the pump & pump motor to ensure the proper accumulator pressure through solenoid valves brake wheel cylinders of each wheel.

How!!!!!.....

Existence…Hill-start Assist

Control is available on a number of Toyota models including Fortuner, Prius, Land Cruiser, RAV4 and 4Runner, Honda C-RV and also in Volkswagen Touareg.

Downhill Assist Control is standard equipment on Toyota Fortuner, Land Cruiser, RAV4 and 4Runner.

Advantages & limitations….Prevents accidents while starting

the vehicle on slopesCost effective solutionStress free drivingLonger clutch lifeIt’s a advantage for heavily

loaded vehiclesIt is suitable for only manual

transmission.

Conclusion:By devising a mechanism of this sort we

could make driving more easier and most importantly this sort of technology could reach the common man who form the majority in any economy.