AVCSS - Advanced Rotary Plow

Advanced Rotary Plow (ARP)
Vehicle Control

Han-Shue Tan
Associate Research Engineer, California PATH
hstan@path.berkeley.edu

In 2000, PATH started an Advanced Rotary Plow project with the California Department of Transportation (Caltrans). The Caltrans ARP is applying PATH's automated steering using magnetic markers to safely position the blower near the guardrail in areas where magnets have been installed. This will be the first automated vehicle in the United States that will be ready to be driven on highways by operators performing real functions under real operational conditions.

The advantages to the system are twofold:

1) Increases operational safety

The driver knows where the guardrail is without having to "drive by feel".

It reduces driver fatigue by allowing him to concentrate on the plow and not where the guardrail is.

It increases safety in areas that have steep ravines or canyons.
2) Reduces maintenance costs

It reduces wear and tear on guardrails since the driver no longer needs to "drive by feel".

It reduces wear and tear on the plow by reducing guardrail contact.

A conventional snowblower (Kodiak Northwest single engine rotary snowplow with full hydrostatics) was modified to include:

a computer data acquisition and information processing unit

sensors for measuring steering angle and vehicle movements

sensors for measuring the field of magnetic markers installed in the roadway

steering wheel actuator

driver-vehicle interface (DVI).

Two primary technologies are being used in the ARP: detecting the plow's position relative to the guardrail and automatic steering 4 inches from the guardrail. Sensors underneath the blower detect magnets on the road near the guardrail: a front magnetometer array with 6 magnetic sensors was first installed in front of the front tires, then a rear one with seven magnetic sensors behind the rear tires. Signal processing of the magnetometers provides lateral position measurement relative to the guardrail and yaw angle estimate. Binary coding of the magnetic markers when installed (north pole up vs. south pole up) also provides information about guardrail characteristics, e.g. shoulder side (right or left of the blower) and end of guardrail.

When the blower is positioned correctly, the system allows the driver to switch to automated steering for the duration of the guardrail. For this, the operator has to use the transition toggle switch located under the radio. The driver is helped by two displays located in the cab:

the guidance lights, underneath the voltmeter, display the position of the blower with regard to the guardrail.

the status lights, underneath the air filter indicator, display what the system is doing at any point in time.

The guidance indicators display the blower head position with respect to the guardrail. They act differently depending on which side the blower is operating on (the above picture shows the guardrail on the right hand side). The correct position is reached when the green light (with the line through it) closest to the guardrail is lit. Each LED represents 4 inches separation on the ground. If any of the far red lights is lit, it means the blower is too close to the guardrail: the right red LED means the blower is too close to the guardrail on the right, the left red LED the blower is too close to the guardrail on the left. Also, the blower must maintain a speed of between 1 and 8 mph to be able to do auto steering. If the speed is too low, the top red LED (speed up) will lit or flash. If the speed is too high, the bottom red LED (slow down) will lit.

PATH also installed a audible unit to sound three sounds:

acknowledgment (transition to auto steering)

end of magnets (end of guardrail)

emergency (take over control now).

There are four status lights:

Auto - Blue On: auto steering is on.
Flashing: system on and auto steering is pending.

Ready - Green On: system on and able to transition to auto steering. Beep will sound.
Flashing: system booting up (occurs only when the vehicle is first started).

Manual - White On: system on and under manual control.
Fault - Red On: problem with the system, driver won't be able to transition to auto steering.
Flashing: emergency takeover. Repeating beep will sound, driver needs to resume manual control.

TEST SITE

Currently, PATH has a single implementation site:

Donner Summit on I-80 (Lake Tahoe), CA. (7239 feet)

Magnets were installed along the eastbound and westbound guard rails of Interstate 80 in 2001, at 1.2 meter spacing and 4 feet away from the guardrail. There are 5 sections on the westbound shoulder and 3 sections on the eastbound shoulder, between Soda Springs and Kingvale. The total length of magnets is about 1 mile.

SCHEDULE

December 2002: prototype hardware completed and first software installed (Berkeley)

March 2003: system initial validation (Kingvale)

April 2003: trial runs with operators (Kingvale)

October 2003: demonstration (Kingvale)

Winter 2003/2004: first winter field testing and evaluation (I-80)

Summer & Fall 2004: prototype system evaluation, redesign and human factors review (Berkeley)

Winter 2004/2005: winter field operational tests (I-80)

DEVELOPMENT TEAM

Control: Han-Shue Tan, Fanping Bu

Software: Bénédicte Bougler, Paul Kretz

Hardware: David Nelson, Thang Lian, Bart Duncil

Human Factors: Joanne Lins

DEMONSTRATIONS

PATH, AHMCT and Caltrans workshop at Kingvale, CA. October 15, 2003
The blower was driven along 150 meters of cones representing the guardrail in the Kingvale yard.

MOVIES

Automated Snowblower
Kingvale Yard, October 2003

3.38 min

PUBLICATIONS

Article in the San Francisco Chronicle published on October 29, 2001: Highway work going high-tech - UC Davis constructs futuristic equipment by Michael Cabanatuan.