Chapter 11: Advanced Braking Systems Automotive Brake Systems Chapter 11: Advanced Braking Systems

Understand and Describe: Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Objectives Understand and Describe: How fatality rates for miles traveled have been reduced The history of stability control through ABS/TCS systems The need for stability control systems The purpose of each of the stability control sensors Active braking

Understand and Describe: Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Objectives Understand and Describe: Cruise control systems that utilize active braking The operation of a regenerative braking system on a hybrid vehicle

Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Introduction Automotive technology has been constantly evolving and improving for over 50 years 1960’s – Development of emission control systems 1970’s – Increased fuel efficiency in response to fuel shortages 1980’s – Increase overall efficiency and performance via fuel injection 1990’s - Present – Vehicle safety has been a primary focus Fatality rates per 100 million miles traveled have fallen from 5.5 in 1966 to 1.1 in 2010 Advanced braking systems rely on ‘real time’ communication via fast computers and networks

Introduction Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Introduction Chart showing examples of various manufacturers’ names for their ESC systems. (Image – Shop Manual Pg. 500)

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems ABS was the first major development in stability control Provide greater driver control under heavy braking Early systems dealt with rear wheel lock-up Became especially important on front wheel drive vehicles and unloaded pickup trucks Rear wheel lock-up tends to cause vehicle spin Three and four channel ABS added protection against front wheel lock-up Front wheel lock-up causes a loss in steering

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems Traction control systems were a natural evolution of ABS Used many of the same components Helps control wheels that are spinning too fast Reduce engine torque Apply brakes to drive wheels (Image – Classroom Manual Pg. 249)

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems Electronic steering systems Early systems used a solenoid to control P/S pressure Allowed greater assist at low speeds and better road feel at higher speeds Controlled based on VSS and/or driver input Top Image – Typical Steering Angle / Rotation Sensor. Bottom Image – Typical solenoid used to control hydraulic P/S system pressure. (Images – Classroom Manual Pg. 250)

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems Electronic steering systems Late model vehicles often use an electric motor for steering assist Located on the steering column or steering rack Controlled similarly to older systems to provide proper assist Top Image - Typical steering column mounted electronic power steering system. (Image – Classroom Manual Pg. 250) Bottom Image – Typical rack mounted electronic power steering system. (Image – Shop Manual Pg. 505)

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems Tire Pressure Monitoring Systems (TPMS) Low tire pressure poses a great safety hazard and can prevent stability control systems from operating to their full potential Early systems used ABS wheel speed sensors to determine low tire pressure Low tire has a smaller rolling diameter and must spin faster Modern systems use tire pressure sensors installed in each wheel Wirelessly report tire pressure information to the TPMS module Sensors may need to be ‘re-learned’ if tires are rotated

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems A typical valve stem mounted TPMS sensor. (Image – Classroom Manual Pg. 251)

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems Stability Control Modern stability control systems apply and release the brakes of the correct wheel(s) at the correct time to maintain vehicle control during hard maneuvering Help prevent loss of steering control due to understeer and oversteer through a corner ABS, TCS, and Stability Control systems all rely on tire condition Bald tires may cause false activation of these systems and unsafe conditions

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems Understeer Vehicle does not turn as tight as the driver intended and moves towards the outside of the road Usually caused by loss of traction on the front wheels (Image – Classroom Manual Pg. 252)

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems Oversteer Vehicle turns tighter than the driver intended and begins to spin Usually caused by loss of traction on the rear wheels (Image – Classroom Manual Pg. 252)

Stability Control Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Systems Animations comparing understeer vs. oversteer both with and without electronic stability control systems. Click on images above to play animations

What was the first type of ABS used? Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Answer: Rear Wheel ABS (a.k.a. RABS or RWAL) What was the first type of ABS used?

Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Answer: TPMS (Tire Pressure Monitoring System). Early versions of this system relied on wheel speed sensor inputs, while modern versions use pressure sensors.

Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Answer: Oversteer. _____________ is a stability control condition where the vehicle is likely to enter a spin.

Stability Control Hardware Automotive Engine Performance, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Hardware Steering Angle Sensor Measures driver input Direction, speed, and angle of steering wheel rotation System may need to re-learn the straight ahead position of the steering wheel after some service Typical Steering Angle / Rotation Sensor. (Image – Classroom Manual Pg. 250)

Stability Control Hardware Automotive Engine Performance, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Hardware Yaw Rate Sensor Measures vehicle movement Determines how the vehicle is actually turning Electronic Stability Control (ESC) module compares yaw rate to driver input to determine if correction is necessary Typical yaw rate sensor. (Image – Classroom Manual Pg. 252)

Stability Control Hardware Automotive Engine Performance, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Hardware G-Sensor Also called a lateral accelerometer Measures rate of acceleration and direction of movement Yaw or G-sensors may use mercury switches or beam-type hall-effect sensors Typical lateral accelerometer / G-sensor. (Image – Classroom Manual Pg. 252)

Stability Control Hardware Automotive Engine Performance, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Hardware Hydraulic Modulator Contains valves used to isolate, increase, or decrease pressure to wheel brakes Can also contain pump motor and module Module may provide ABS, TCS, and ESC functions Typical hydraulic modulator assembly. (Image – Classroom Manual Pg. 253)

Stability Control Hardware Automotive Engine Performance, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Hardware Throttle Actuator Control Also called Electronic Throttle Control ESC module may request ECM/PCM to reduce throttle angle Reduces engine torque Typical throttle actuator control / electronic throttle control assembly. (Image – Classroom Manual Pg. 253)

Stability Control Hardware Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Hardware Roll Control / Ride Control Automatic Ride Control (ARC) systems can control shock absorber / strut operation to prevent body roll in hard turns May also increase stability at higher speeds Reduce compromise between vehicle stability and ride comfort Some systems use air springs or air shocks to adjust ride height and suspension stiffness Networking The ESC module communicates with other modules such as the instrument cluster and ECM/PCM Allows for control of warning lights, shared information from vehicle sensors, and reduction of engine torque when needed for vehicle stability

Stability Control Hardware Automotive Engine Performance, Sixth Edition Chapter 11, Advanced Braking Systems Stability Control Hardware Typical air spring assembly. (Image – Classroom Manual Pg. 254)

Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Answer: Direction of rotation; speed; angle. What three pieces of information does the steering angle sensor provide?

Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Answer: Yaw Rate. The stability control module compares information from the steering angle sensor to the ______ ______ sensor to determine if the stability control system must activate.

Active Braking Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Active Braking Systems Active Braking Systems use electronic controls to further reduce the possibility of a collision May use cameras or radar sensors to sense vehicles or other objects in the vehicle’s path and warn the driver May ‘pre-charge’ the brakes to allow for faster braking once the driver steps on the brakes in response to the warning May also control pressure to prevent excessive braking that will lead to wheel lock-up May be used as part of an active cruise control system that will automatically maintain a set distance from the vehicle ahead Some systems may automatically apply the brakes without any driver intervention in order to prevent a collision

Active Braking Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Active Braking Systems Illustration showing how radar sensors can detect vehicles ahead. (Image – Classroom Manual Pg. 255)

Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Answer: Active. _________ braking systems can either apply the brakes, or prepare the brakes for application without any input from the driver.

Regenerative Braking Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Regenerative Braking Systems Regenerative braking systems convert kinetic energy into electrical energy during braking Reclaims energy normally lost to heat using traditional friction braking Can help slow the vehicle, but traditional brakes are still responsible for stopping the vehicle Used on hybrid and electric vehicles Regenerative braking systems use a motor as a generator during braking or deceleration

Regenerative Braking Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Regenerative Braking Systems Toyota Prius Motor/Generator (MG) 1 acts primarily as an engine driven generator to keep the high voltage battery charged MG 2 acts as a motor to power the wheels or assist the gas engine Also acts as a generator for regenerative braking Kia Optima Uses a belt-driven starter/generator Chevrolet Volt Electric motor drives the wheels and acts as a generator during braking Gas engine used primarily as a generator

Regenerative Braking Systems Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Regenerative Braking Systems Kia Optima Belt-Driven Starter-Generator. (Image – Classroom Manual Pg. 256)

Automotive Brake Systems, Sixth Edition Chapter 11, Advanced Braking Systems Answer: Hybrid; Electric. Regenerative braking systems are used on __________ and __________ vehicles.