Precision Point Blog

Explanation of Wheel Angle Sensors and why they are Important

by Kerri Birdwell on June, 28 2013 in Guidance & Steering

It seems that the question has been raised as to why wheel angle sensors are required on GeoSteer installations as well as recommended on ParaDyme installations.  As such I am going to take some time this week to explain what a wheel angle sensor does, why it is important and how to get it just right.

When using integrated hydraulic steering systems such as the ParaDyme and GeoSteer, wheel angle sensors are important for achieving the highest level of accuracy.  A wheel angle sensors job is to know the exact location of the steering wheels or articulation point.  This allows the system to know your exact GPS position using the receiver as well as the exact position of the wheels.  Without a wheel angle sensor you will still have your exact GPS position but the system has to guess which direction the wheels are pointed based off of changes in the vehicle heading while moving.

Wheel angle sensors are not required for use with the ParaDyme but are always recommended and especially for self-propelled sprayers, floaters, any vehicles traveling less than 2 mph or more than 10 mph as well as steer ready vehicles that come equipped with them.  Since the GeoSteer has one GPS antenna, a wheel angle sensor is required for all GeoSteer installations. As such knowing the exact position of the steering axle is imperative.

Wheel angle sensor installation varies for different vehicles.   The specifics for each installation are included in its corresponding install guide.  Correct installation of the wheel angle sensor and adequate counts are critical to provide a high resolution of the steering wheels position.  It is good to remember that the values and exact positions suggested in the install guides may need to be modified to prevent damage to the vehicle and/or wheel angle sensor.  There are number of variations that can occur on the same make and model of vehicle.  As such it is the responsibility of the installer to be sure that the wheel angle sensor is installed correctly with adequate counts for their particular vehicle.  Prior to turning the wheels it is important to makes sure that the wheel angle sensor can move freely.

Install guides suggest what length to cut the rods as well as the length the rods should be at assembly.  Wheel angle sensors provided by Ag Leader should have counts ranging from 5000 to 60,000.  The number of counts can be adjusted by changing the linkage arm length.  Shortening the linkage arm will gain more counts, lengthening the linkage arm will reduce the overall counts.  The counts should also be even left of center and right of center, within 5000 counts, and have no skips or jumps.  Uneven counts can cause serious steering accuracy problems.  An example of this would be having 30% of the counts left and 70% right.  If simply adjusting the linkage rod arms does not fully even out the counts, the potentiometer can be adjusted in the housing as well.

Kerri Birdwell

Kerri Birdwell came on board with the Machine Guidance Support team in October 2011. She is the Pacific Coast Field Support Technician. She provides technical support in the field and on the phone. Kerri graduated from Cal Poly, San Luis Obispo in 2009 with a degree in Agriculture Systems Management. After college she spent two years in the irrigation industry designing and making scheduling recommendations. Kerri was raised on a cattle ranch in Coalinga CA where she still spends the majority of her free time. She enjoys riding horses, hiking and being at the beach.

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