Efficient Modeling of Automatic Gear Selection Using ... · PDF fileEfficient Modeling of...

Confidential | Shivakumar | 10/7/2014 | © Robert Bosch Engineering and Business Solutions Limited 2014. All rights reserved, also regarding

any disposal, exploitation, reproduction, editing, distribution, as well as in the event of applications for industrial property rights.

Efficient Modeling of Automatic Gear Selection Using MathWorks Tools

Shivakumar Katukam

Nagesh Srikanth

Rajeev P A

Transmission Control Systems development

Robert Bosch Engineering and Business Solutions Ltd


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Confidential | RBEI/SAM-MKT | 10/7/2014 | © Robert Bosch Engineering and Business Solutions Limited 2014. All rights reserved, also

regarding any disposal, exploitation, reproduction, editing, distribution, as well as in the event of applications for industrial property rights.

About RBEI

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Facts &

figures

2013 data

154 Patents filed


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Objective

To develop Control software for Automatic Transmission system

Within a short time (starting from scratch)

To reuse this SW as a platform that is easily customizable to

different gearbox & vehicles


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• Code Generation

• Flashing on controller

• Testing

Hardware Simulation

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Control Model

Control Model

validation

Gear Box

Model

Vehicle Model

Simulink Integrated model with controller

and vehicle environment

• Getting real time inputs

• Providing to integrated model

• Testing

PC Simulation

Embedded Coder

SimDriveline

SimDriveline /

SimHydraulics



Agenda

Transmission Overview

Transmission Classification

Step Automatic Transmission

Transmission Control Unit

Gear Selection Strategy

Integration and Testing

Conclusion


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Transmission Overview

Picture from How Stuff Works

Transmission is a link between engine and wheels

Transmit power from the engine to the driving wheels at an

appropriate speed

Provides more than one gear, without this cars would be limited to

one gear ratio


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Transmission Classification

MT(Alto 800) AT(Verna) AMT(Celerio) DCT(Octavia) CVT(Jupiter)

Automatic Transmissions


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Step Automatic Transmission


Three major Automatic Transmission configurations are

Simpson planetary gear sets

Ravigneaux planetary gear sets

Lepelleiter planetary gear sets

These configurations can be modeled using MathWorks SimDriveline

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Transmission model using MathWorks SimDriveline

A B C D E

R T F F T F

1 F F T T F

2 F F T F T

3 T F T F F

4 F T T F F

5 T T F F F

6 F T F F T

T - Engaged

F - Disengaged


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Transmission Control Unit

Transmission control unit software modules

Gear

selection

Shift

coordination

Shift

actuation

Communications module

Diagnostics

HW I/O


Decide when and how to change the gear in the vehicle for optimum

performance, fuel economy, reduce emission and enhances shift quality

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Gear Selection Model


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Gear Selection Strategy


Gear Selection module determines the most appropriate gear for the

current driving conditions

This module is modeled using MathWorks Simulink

Gear selection module evaluates a number of functionalities like

Depending on the active function, a shift-map corresponding to that

function is selected

Map selects the next gear by checking driver demand and output

shaft speed

Heavy Braking

Fast-Off Hill

Detection Kind of Driver

Hot- Mode detection

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Inputs

needed for

gear

calculation

Inputs from Driver,

Engine and

several

sensors

Static Drive

Program

Dynamic Drive

Program

Road functions

Mode Control

Gear Box controller to control

combination of clutches

Gear request

Shift prevention

Dynamic

Gear request

Target Gear

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Gear Selection Strategy Overview



HEAVY BRAKING


Objective of this module is to detect a heavy braking condition in the

vehicle

Once heavy braking is detected corresponding shift map helps to

shift the gear down quickly to assist the vehicle to stop immediately

The following signals are continuously

monitored to detect the condition

Brake status(Active/not active)

Output shaft speed

Output shaft speed gradient Accelerator pedal signal

Gear and lever position

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Validation Results Heavy Braking

As soon as Heavy Braking condition is detected, down shifting of gear to minimum gear

is done in a very short time compared to general situations


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HILL FUNCTION


The task of the hill function is to detect the loading of the vehicle and to

react to the different loading situations

Two levels of downhill and three types of uphill condition can be detected

and the gear shift point evaluation can be changed accordingly

Depending on the type of hill

detected, shift map corresponding

to that hill is chosen to select the

appropriate driving gear

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FAST-OFF


The task of the Fast-Off function is to detect large negative pedal

gradients and to prevent up-shifts in this situation for a predetermined period of time

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Validation Results Fast-Off Function

Fast-off function has detected the sudden negative pedal and prevented the

up-shift of gear


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HOT MODE FUNCTION


The objective is to evaluate the high temperature conditions based on

the vehicle load and transmission fluid temperature. In this situation,

the software recommends to shift the gear down and to increase the

engine rpm to cool the fluid at higher rate

Three level of Hot mode

condition is evaluated. Hot mode

plain, Hot mode hill1 and Hot

mode hill2

Gear shift point is changed according to criticality

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KIND OF DRIVER


The objective of Kind of driver module is to evaluate the type of driver

(Extreme Economy, Economy, Sporty, Extreme Sporty) by analyzing the accelerator pedal signal

Final outcome after the

evaluation is a counter value,

through which type of driver

can be evaluated

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Validation Results Kind of Driver

Depending on usage of accelerator pedal, counter value varies and if the counter value

is high then driver is classified as sporty and if it is low then economic

Extr. Economy Economy

Sporty


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Integration and Testing


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Validation Results Normal Driving

The Gear from model is very close to the actual gear from vehicle


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Conclusion


Signals from real AT vehicle were fed as inputs into the model and the

results achieved were similar to genuine automatic gearbox behavior

The availability of physical components in the SimDriveline toolbox

helped to customize the models for different vehicles quickly

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