Lateral Control for Snow Blower

1
Lateral Control for Snow Blower

• PATH Conference
• Oct 25, 2002
• Han-Shue Tan

2
Snow Blower

• What is a snow blower?

• What does it do?

• Why steering control?

3
Advance Rotary Plow (ARP) Project

• Organization and Responsibilities
• Caltrans
• Overall management and coordination
• PATH, UC Berkeley
• Automated steering system design development
• System architecture design, hardware
  installation, sensor signal processing, control
  algorithm and HMI development
• AHMCT, UC Davis
• Feasibility studies
• Radar warning system, GPS system, rotary
  protection
• Current implementation schedule
• Blower reached RFS 6/25/02 (kick up meeting
  7/18/02)
• Hardware installation and software drivers
  10/31/02
• First system deliver 11/02
• First winter operational test 12/02-3/03
• Second system deliver 10/03
• Second winter operational test 11/03-3/04

4
ARP Lateral Control Goals

• Automated steering along guardrails

• 2-4 tolerance
• Less than 2 effective sensor range

• Uncertain operation initialization termination
  (30/10m)
• Variable front tire normal load (shoe position)

• Rear wheel steering operation

• Large and variable snow removal force
• Uncertain snow chain effects
• Foreign forces (snow, ice, debit, guardrail)
• Driver intervention (intentional and
  unintentional)
• Smooth and easy transition
• Simple operator/safety assistance (warning
  indication)
• First automated vehicle on highway by operators
  with real functions under real conditions

5
ARP Lateral Control Design Difficulties

• Control
• Extreme high control gain
• No preview, short start-up, immediate transition,
  very low vehicle speed, extreme large
  uncertainties and disturbances
• Nonlinear operating conditions
• Uneven regulation position, random driver
  intervention, rear steering variations, tire
  chain effects, backlash and variable hydraulic
  assist
• Operational
• Operator change operating condition at will
• Speed (stop and go), work load, tire normal
  force, switching conditions, driver emergency
  response, small correction
• Harsh and demanding working environment
• Safety
• Fault detection and management
• Warning and redundancy
• Environmental
• Senor and computer survive under snow, ice, salt,
  dirt, and hot and code water
• Timing and resources
• Demo 2003 and limited preparation/access time
  before winter

6
ARP Lateral Control Design Philosophy

• Design
• As simple as possible
• Process
• As efficient as possible (minimizing error)
• Performance
• As good as feasible (minimizing assumptions)
• Operation
• As many scenarios as possible, as safe as
  possible
• Operator
• As transparent as possible
• Equipments
• Use existing system if possible, reduce number of
  sensor as possible
• Mind set
• Problem solving (every problem counts)
• Emphasis
• Weakest link, sound engineering judgment

7
ARP Lateral Control Hardware Configuration
8
ARP Lateral Control Design Tasks

• System Design
• Requirements
• Configuration
• Hardware/Software Development
• Sensors and signal processing
• Actuator
• Computer and drivers
• HMI circuit and HMI components
• Wiring and weather proof
• Analysis
• Blower model
• Tire chain effects
• Driver characteristics
• Control Algorithm
• Steering actuator
• Lateral tracking
• Automated/manual Transition

• HMI design
• Operational analysis
• Driver guidance
• Indicators
• Warning system
• Safety
• Robustness
• Fault detection
• Failure mode
• Warning design

9
ARP Lateral Control System Configuration
10
Blower Modeling Issues
11
ARP Steering Actuator Design

• Hardware
• DC motor (with clutch), PWM current control
• Position servo capability
• Safety
• Fail to no torque, self-diagnosis
• Driver interface
• Back driven

• Software
• Initialization
• Self calibration
• Servo position
• Torque command
• Multi-mode transition
• Multi-mode control
• Fault detection management

12
ARP Lateral Control Initial Results

• Basic control concept
• Look-ahead prediction
• High gain feedback (no preview)
• Unknown rear steering angle
• First day results
• No tuning
• Different (unknown) rear steering angle
• Needs
• Control re-design
• Proper Initialization
• Transition capability
• Variable controller modes
• Weight and disturbance effects
• Chain effects

13
ARP Lateral Control HMI Design

• Principle
• Simple, transparent, natural, safe

• Current design
• Switches
• Auto/manual 2-way toggle switch
• Actuator kill switch
• Indicators
• Control indicators (manual/automated,
  fault/system ready, automated ready, automated
  pending)
• Guidance indicators (left, right, center, speed
  up, slow down)

• Audible warning
• Emergency
• Take over control
• Acknowledgement
• HMI circuit
• Heart beat, additional redundancy

• Driver override
• Stop go, emergency, correction

14
The ARP Lateral Team

• Caltrans
• Robert Battersby, Kirk Hemstalk, District 3 4
• Hardware design installation
• David Nelson, Thang Lian, Bart Duncil, Scott
  Johnson
• Steering actuator control and system design
• Fanping Bu, NSK
• Software development
• Benedicte Bougler, Paul Kretz
• HMI design and Human factor analysis
• Joanne Lins
• Modeling and tire chain effects
• Shiang-Lung Koo

15
Conclusions

• ARP A straight-forward automated steering
  control application?
• Complicated and difficult!
• Current goals
• Installed a functional blower steering control
  system
• Conduct feasibility testing (under real operating
  environment)
• Provide base for 2003 improvement
• A (first) good deployment experience for future
  vehicle automation