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Advanced Control Functions of Decoupled Electro-Hydraulic Brake System

Presentation on IEEE AMC 2016 Workshop, Auckland, New Zealand

Valentin Ivanov

on 4 May 2016

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Transcript of Advanced Control Functions of Decoupled Electro-Hydraulic Brake System

Advanced Control Functions Of Decoupled Electro-Hydraulic Brake System
2016 IEEE 14th International Workshop
on Advanced Motion Control
Auckland, New Zealand, 22-24 April 2016

Dzmitry Savitski, Valentin Ivanov, Dmitrij Schleinin, Klaus Augsburg
(Technische Universität Ilmenau, Germany)
Thomas Pütz
(ZF - TRW, Germany)
Chih Feng Lee
(Linköping University, Sweden)

System Introduction
Wheel Slip

Disturbance Rejection
Brake Judder

Coupled Brake System
Brake pedal
is coupled (hydraulically connected) to
brake calipers
Decoupled Brake System
Brake pedal unit with
master cylinder and pedal simulator
control unit
Pedal sensor
Replacement of traditional brake actuation system
Provides emergency and safety functions (ABS, ESP…)
Easy integration into Electric & Hybrid Vehicles (Decoupled Brake Pedal)
Decoupled System Architecture
1 – Brake pedal unit, 2 – Electro-hydraulic control unit (EHCU),
3 – Front wheel brakes, 4 – Rear wheel brakes, 5 – High pressure accumulator,
6 – Boost valve, 7 – Pedal simulator, 8 – Normally open base brake valve,
9 – Normally closed base brake valve, 10 – Isolation and dump valves
Brake Application

Brake demand (pressure) is defined by pedal travel sensor

Pedal Feel

Pressure in the master cylinder provides feedback force to the driver during base and regenerative braking

Purposes of Advanced Brake Control
- Continuous wheel slip control

- Base brake control with brake feel adaptation and
disturbance rejection

- Active brake judder compensation
Continuous Wheel Slip Controller
Control error by wheel slip
Control torque by PID and ISMC control
Test Results - Continuous Wheel Slip Control
Braking on
Braking on
Smooth and precise tracking of the wheel slip ratio
High braking performance
Robustness to variation of road friction conditions
No chattering effect
Characterization of Brake Pedal Feel
Brake Pedal Feel: Target and Deterioration
Goal: No pedal force variation within the whole operational range of the brake pressure
Deterioration due external disturbances
Processes during driving cycle
Rapidly changing processes
Long-term processes
Vehicle mass variation
Road grade
Front wind
Rolling resistance
Brake pad / disc wear
Tire wear
Disturbance Compensation Architecture
Road Grade Compensation
Reactive brake torque
Slip control torque
Maneuver specifications:
- Driving downhill with road grade of -20%
- 3 brake applications with different reference deceleration

Assessment criteria:
- Pedal workload
Compensation of Brake Friction Change
brake torque
brake torque
Correction factor is estimated by RLS method
Stepwise alteration of correction factor using set of rules
Friction coefficient is reduced
Correction factor
for brake demand is adapted
Pedal travel is compensated
Case Study

Maneuver specifications
Set of brake applications from 100 km/h with reference deceleration 0.4 g
ISO26867 procedure is used
Assessment criteria
Deviation between actual and reference deceleration as integral time absolute error
Brake Judder Phenomena
Geometric imperfections on brake rotor surface cause periodic variations in brake torque (brake judder)
The brake judder means vibrations felt in the brake pedal, vehicle floor and/or steering wheel
Brake torque variation as function of brake rotor geometry (approximate using Fourier Series):
Attenuation goal:
Active control on brake clamp force to compensate brake torque variation
Attenuation Procedure
Reduce Brake Torque Tracking Error
Actual brake torque
Reference brake torque
(by pedal dynamics)
Step 1:
Brake system model and judder in state-space form
Step 2:
Observer-based algorithm
Step 3:
Selection of controller gains

Test Results - Brake Judder Attenuation
Brake torque variation without (top) and with (bottom) compensation at various frequencies
Avoidance of control effects overlap: Increased system reliability
Benefits of advanced control functions of decoupled electro-hydraulic brake system
Future Works
This work is supported by the European Union Horizon 2020 Framework Program,
Marie Skłodowska-Curie actions,
under grant agreement no. 645736
Continuous wheel slip control: Braking distance reduction and improvement of ride comfort simultaneously
Integrated SMC: Improved system robustness
Disturbance rejection: Consistent brake pedal feel
Adaptive control of EHB system: Brake judder compensation
Brake Judder Phenomena
Geometry (e.g. disc thickness)
Problem of Wheel Slip Control
Seeking for optimal slip in the area of maximum tyre-road friction
Common approach: rule-based control of brake torque
Full transcript