1. NEW DEVELOPMENTSIN AGRICULTURAL EQUIPMENT TRACTORS
R. T. Schuler
National AgrAbility Project
University of Wisconsin - Madison
The following discussion will focus primarily on new developments in Agricultural tractors. Topics include guidance/steering, transmissions and seating.
November 14 , 2006

2. Tractors Guidance and Auto-Steer Global Positioning System Guidance
Autonomous
Transmissions
Number of gears/speeds
CVT - Continuously Variable Transmission
IVT - Infinitely Variable Transmission
Suspension
Tractor Chassis
Cab
Seat
The guidance/ auto steer requires the global position system established by the US government primarily for military purposes. Signals from these satellites are available without charge. Guidance systems have a display that informs the tractor operator the distance that he/she is off course and then can make a steering correction to get back on course if an error exists. Auto-steer allows the error signal to be used to correct errors automatically for the operator. Autonomous operation is allowing the tractor to operate in the field without an operator. Technology is available but safety issues exist for introducing this technology to the marketplace.
Tractor transmissions have changed over the years with respect to the number of speeds available from one or two to 24 to an infinite number of speeds. As these changes occur, the need for the operator to use his/her feet have been reduced. In some cases for normal operation the only time the operator needs to use his/her feet is when starting the engine when the foot operated clutch may need to be disengaged
Tractor suspension systems have been designed to improved the comfort of the operator The ground induced vibration is reduced by the tires, tractor suspension (e.g. support springs at the front axle), cab mounting and seat support (new is the active tractor seat).
The picture of the tractor illustrates a guidance system..

3. Global Position Systems
Basic GPS
Satellite System Only (3 of 24)
Low cost – automobiles
Error – 100 feet
The earth is surrounded with a constellation of 24 satellites which serves as the global positioning system. This systems provides signals to GPS receivers which can used to locate a person’s position on earth with respect to longitude and latitude. Using this system of satellites, errors of 100 feet will occur, which is reasonable for some uses such as automobiles. The errors are caused by clock errors, atmospheric conditions, air temperature plus others.
The photo shows the earth and the constellation of 24 satellites which are equally spaced around the earth.
Satellite Constellation

4. Global Position Systems
Basic GPS
Satellite System Only (3 of 24)
Low cost – automobiles
Error – 100 feet
Satellites plus free beacon
Intermediate cost
Error – 2 to 3 feet
To reduce the errors in the satellite constellation, differential correction is required. Diagram shows four satellites, differential correction beacon on earth’s surface and a tractor or other mobile equipment with GPS receiver on the earth’s surface. The beacon provides a correction signal which reduces the error to 2 to 3 feet. The receiver obtains signals from the four satellites and the beacon transmitter which provides a correction signal. Most of the beacon transmitters are located along waterways e.g. Oceans, Gulf of Mexico, Great Lakes and Mississippi River. This correction signal is received without cost.

5. Global Position Systems
Basic GPS
Satellite System Only (3 of 24)
Low cost – automobiles
Error – 100 feet
Satellites plus free beacon
Intermediate cost
Error – 2 to 3 feet
Satellites plus geostationary satellite
More costly
Error – 3 to 5 inches
US companies have launched geostationary (retain a stationary position in the sky with respect to the earth’s surface) satellites which provide a correction signal for a fee. Errors are from 3 to 5 inches.

6. Global Position Systems
Basic GPS
Satellite System Only (3 of 24)
Low cost – automobiles
Error – 100 feet
Satellites plus free beacon
Intermediate cost
Error – 2 to 3 feet
Satellites plus geostationary satellite
More costly
Error – 3 to 5 inches
Satellites plus base station nearby
Costly ($18,000 in 2006)
One inch or less
The most accurate positioning system uses the satellite constellation and a base station using RTK (Real Time Kinetics) which allows for errors of one inch or less. Before mid 2006, a farmer who wanted to establish a system with this accuracy needed to purchase a portable station which was supported by a tripod with a system cost of $18,000. Recently (summer of 2006) companies and in many cases groups of farmers are constructing networks of RTK towers and sharing the costs with the farmer users. The charge for this service depends on the number of tractors and number farmers participating e.g. $ a one time fee and then annual fee of $1000 for one tractor and $1500 for two tractors. In the picture is a tractor with guidance/auto-steer system with a RTK unit on a tripod in the corner of the field.

7. Guidance and Automatic Steering Adoption
Most systems use GPS
Payback
Improve productivity
Increased forward speed
Reduced crop inputs
Reduced operator fatigue
Ability to operate longer hours (darkness)
Simple installation – 30 minutes
Lower cost in recent years
Nearly all systems use the satellite constellation. Productivity is improved because the operator is able minimize overlap with successive passes when operating in the field and reduces the area skipped (negative overlap) during successive passes. By having less overlap, the inputs such as fertilizer, pesticides and lime are reduced. With guidance and more so with auto-steer, the tractor operator can give more attention to the implement attached to the tractor or complete other tasks while in the operator’s seat. This should create less fatigue and allow the operator to work longer hours. Also allows for operation during hours of darkness especially for the wider machines such as sprayers. Some auto-steer systems are easy to install such as those that attached adjacent to the steering wheel. These have a roller which is in contact with the steering wheel. As a result the control system provide a electrical signals and the steering wheel is turned to correct the error. Other auto-steer systems need to be connected into the steering control system. New tractors will have features to make this process simpler. As with anything new the price is high. But as more units are sold, the price will go down.

8. Line A – B is base line called Track 0
When starting a field with a guidance or auto-steer system, the operator must establish a base line by manually steering the tractor at one edge of the field. This is the line between A and B. By inputting the proper machine operating width, accurate parallel passes will be made and a rectangular field can be covered. Irregular shaped fields require manual operation in some areas of the field.
Line A – B is base line called Track 0
Guidance provided between points A and B

9. Example of a Light Bar Located in front of operator
All lights on in test mode
One example of a system to inform the operator of the degree of error is a lightbar. In the test mode all the lights are on across the bar, red at the ends (large error), green in the middle, and yellow in between the red and green. The photo in the upper right hand corner shows a light bar unit that has a small information screen. The figure in the middle of the slide illustrates all the lights on the lightbarilluminated in the test mode.
Green light – acceptable area
Yellow light - caution area
Red light - unacceptable

10. Middle green light is on- Driving right on target
Light Bar
Middle green light is on-
Driving right on target
When driving right on target, the middle green light is illuminated. Lower figure illustrates all lights illuminated and upper figure is the lightbar with only middle green light illuminated.

11. Light Bar Right most green light is on:
Driving to right of center but acceptable
(error increment can be adjusted)
In this view the green light which is second to the right of the center light indicates there is a small error but apparently is acceptable. The operator could turn the steering wheel so that the center green light is illuminated. Lower figure shows all lights illuminated which is the test mode.

12. Light Bar First yellow light is on:
Caution – corrective steering should be taken
The first yellow light right of center on the lightbar is illuminated indicating the driving error is in the caution area, the operator should consider making a steering correction. The lower figure shows all lights illuminated which is the test mode.

13. Red light is on: Operator needs to make steering correction
Light Bar
Red light is on:
Operator needs to make steering correction
The first red light right of center is illuminated indicating the driver needs to make a steering correction. The lower figure shows all lights illuminated which is the test mode.

14. Another Display System
Green rectangle represents front end of tractor
and angle of line indicates error (magnitude of error also displayed)
This display is used by Deere showing a top view of the front end of the tractor with a line forward of the front end which indicates error by the angle of the line. The diagram shown indicates no error, line is parallel to the direction of travel. The line at the front of the tractor will change in direction as an indication of the degree of error. Text behind (below in the figure) the tractor indicates the error in feet. This may be the test mode because the word ‘error’ is displayed. During operation a number will appear where the word ‘error’ appears.
Track Error
No Error

15. Another Display System
Green rectangle represents front end of tractor
and angle of line indicates error (magnitude of error also displayed)
Audio alarm when error occurs
The added Deere display has changed where the line at the front end of the tractor is now angled to the right indicating the direction of the error and the magnitude of the error is indicated as being ‘2 feet’. Also ‘Small Error’ appears below the symbol is not a part of Deere display. An audio alarm occurs when error is present.
Track Error
Track 2 ft.
No Error
Small Error

16. Another Display System
Green rectangle represents front end of tractor
and angle of line indicates error (magnitude of error also displayed)
Audio alarm when error occurs
The third display added indicates a large error of 5 feet and the angle of the line at the front of the tractor is angled further to the right.
Track Error
Track 2 ft.
Track 5ft
No Error
Small Error
Large Error

17. New Special Feature
Some companies have a feature which corrects for operation on a sidehill (inclined to the right or left). Errors can be as large as 3 feet. The slide shows a rear view of a tractor on a hill, the right side is uphill.

18. New Features – automatic headland turn around
New Special Feature
Automatic turn around on headland
New Features – automatic headland turn around
One of companies (Deere) has a auto steer program where the auto steer will steer the tractor through the turn around at the end of a field. In the other cases the operator has to take control of the tractor for the turns at the end of the fields. Picture shows a tractor with a mounted row crop planter which has just completed a ‘U’ turn at the end of a field. (From Deere)

19. Option with GPS Guidance e.g. lightbar
Several options are available with respect to guidance/auto-steer. Guidance refers to providing visual indications of the steering error so the operator can take corrective action to reduce the error. Picture shows a light bar with small screen under the light bar. Also shown in an earlier slide(#9).

20. Option with GPS Guidance Autosteer Steering wheel control
Auto steer, low cost system using a small roller that is in contact with the steering wheel to control the steering of the tractor. Also it is easy to install this system.

21. Option with GPS Guidance Autosteer Steering wheel control
Steering control system valve
The more desirable and more costly system is to control steering system through steering control valve.

22. Machine Vision – Non-GPS
Machine vision uses a camera which creates an electronic file of the mage which can be analyzed and used to control the steering based on he conditions in front of the machine or tractor. Examples of conditions are crop/no crop conditions for harvesting machines, preceding passes of the machine, crop residue levels. The figure shows a camera at the front of the tractor which sends the image to the navigation computer. The computer also receives a electrical signal from the front wheel indicating steering angle. The steering control valve receives a signal from the computer which actuates the valve if errors exist.

23. Transmissions for Mobile Equipment
Gear
Speed changes in steps
Single power transmission path
Efficiency at part loads dependent on the number of gears
Hydrodynamic
Automotive transmission
Infinitely variable
Not adaptable to high torque
Hydrostatic
Inefficient
Infinitely/continuously variable
Power split in the transmission
Electronic control of transmission and engine for most efficient operation
Since the first farm tractors the transmissions have been modified to provide operator with more and more speed selections. Today, for many models of tractors an infinite number of speeds are available. More speeds allows the operator to match engine power and load for more efficient and productive operation. Please note cars are coming with infinitely variable transmissions.

24. Background-Gear Transmissions
Early Tractors had one or two forward speeds, one reverse
More forward speeds were added
Speed change without clutching-torque amplifier
Synchronized transmission
Shifting on the go
Infinitely/continuously variable transmission
As transmissions developed over the years more speeds became available and changing speeds was made easier with less operator effort and less clutching which leads to less use of the operator’s feet.

25. Single path for the flow of power through transmission
Tractor Engine and Driveline for Two Wheel Drive
Single path for the flow of power through transmission
Transmission
Engine
Axles
This is a block diagram of the tractor drive train going from the power source, the engine, to clutch, transmission, differential, and axle in that order. Each is represented by a rectangle.
Clutch
Differential

26. Infinitely/Continuously Variable Transmission
Power is directed into two paths
Planetary gear systems facilitates this
Power from the two paths are merged
In the past the power path through was a single path. With the infinitely variable transmission there are two paths which are merged at the output of the transmission. A planetary gear allows the splitting or merging of the paths. It also allows the use of a control system that changes the ratio based on some outside factors such as load. For example the transmission may be in a mode to maintain constant speed while varying the engine speed. Two conditions may exist, large load-high engine speed and light load-low engine speed while maintaining the same forward speed.

27. Basic CVT/IVT Transmission
Sun Fixed path
Planetary
Gear Set
(power
split)
Carrier
Output
Ring
Variable
Path
Input
Block diagram of IVT. The input (left side of diagram) represents the power coming from the clutch which is the input to the transmission, in this case more specifically to the carrier for the planet gears of the planetary gear set. The output of the planetary system is divided between the sun gear and the ring gear. The sun output goes to the fixed path to a gear and provides the output to the differential and drive axles (right side of the diagram). The ring gear output goes to the variable path which contains a hydrostatic drive system then to a gear the meshes with the gear on the output gear/shaft. The hydrostatic drive is controlled to maintain some desirable conditions. One example would be to maintain a constant forward while the engine speed (input to the transmission) changes. For fuel efficient operation a control system may reduce engine speed when under light loads but maintain constant forward at the same time.
2 gears

28. Basic CVT/IVT Transmission
Carrier
Fixed path
Sun
Planetary
Gear Set
(power
merge)
Output
Variable
Path
Input
Ring
Block diagram of another IVT system. This diagram is similar to the preceding diagram except the planetary gear system is at the output side of the transmission. The input from the clutch comes into a shaft which is the fixed path to the planetary via the sun gear. This shaft has a gear which drives another gear which in turn provides power through the variable path to the ring gear of the planetary system. The variable path has a hydrostatic unit which is controlled to vary power through this path. This time the power is merged at the planetary system where the output is the carrier for the planet gears.
2 gears

29. IVT/CVT Characteristics
Hand control for forward, reverse, speed changes and stopping
Smooth, seamless shifting
Unlimited speeds from 0.03 to 26 mph (Deere)
Improved fuel economy at reduced load
Reduced load-maintain forward speed with changing engine speed
Need for feet only to start the tractor engine
Cost – $9780 (right side), $10,490 (left side)
The characteristics of the IVT/CVT are discussed.

30. Suspension System Goals
Improve operator comfort and reduce long term health issues
Reduce vibration from traveling over rough terrain
Reduce vibration due engine and drive train vibration
Improve tractor performance
Reduce the potential for power hop on FWD and FWA
Improve contact between wheels and soil surface
Suspension systems have been designed to improve operator comfort and tractor performance. For operator comfort, vibration caused by the terrain, engine and drivetrain are reduced. Tractor performance is affected by the load carried by the tire. Any bouncing or related vibration affect the load on the tire and its tractive performance.

31. Background on seat suspension
First tractor operators had to stand
Seats rigidly attached to tractor chassis
Spring supported seats-passive
Spring plus shock absorbers -passive
Air suspensions seats-passive
Active suspension seats
Operator stations on farm tractor started with operators standing on the tractors without a seat to suspension seats where feel little or no vibration from the tractor chassis.

32. John Deere Active Seat- $3641
An active suspension seat in photo appears to be similar to an air suspension seat. Tractor controls are in the right arm rest. Added cost for this seat is $3641.
John Deere Active Seat- $3641
Source: Dufner and Shick, Deere

33. Source: Dufner and Shick, Deere
Picture shows the important components of the active suspension seat. The accelerometer senses vertical acceleration and provides an electrical signal to the controller. The actuator is an air cylinder that moves the seat up and down relative to the seat mounting platform and its movement is controlled by the controller. As the tractor is traveling through a field the relative position of the seat relative to earth remains constant. The air reservoir provides storage for compressed air needed by the actuator. The control valve assembly provides for adjustment of the controller to meet the operator needs.
John Deere Active Seat
Source: Dufner and Shick, Deere

34. Source: Dufner and Shick, Deere
This bar graph compares the acceleration for the cab, typical air suspension seat and an active suspension seat. The vertical axis is acceleration in terms of ft per sec-sec. One G of acceleration is 32.2 ft/sec-sec. The acceleration input to the cab is about 4.25 while the acceleration for a typical air suspension seat is nearly 3.5. The active suspension seat has an acceleration of about 1.2, much less than the typical air suspension seat.
John Deere Active Seat
Source: Dufner and Shick, Deere

35. Source: Dufner and Shick, Deere
This is a line graph with acceleration plotted against time on the horizontal axis. Two lines are plotted: one for the cab floor and one for the top of the seat having an active suspension system. The lines are cyclic in nature with hills and valleys. The hill tops for the active suspension seat are about one-tenth of the hill tops for the cab platform.
John Deere Active Seat
Source: Dufner and Shick, Deere

36. Tractor chassis suspension
More beneficial for the higher speeds
Front axle suspension – Deere
Front and rear axle suspension - Fastrac
Due to higher travel speeds, manufacturers are adding suspension systems on farm tractors between the tractor axles and tractor frames. Deere has a suspension system available for the front axle while Fastrac has suspension system for front and rear axles. These suspension systems absorbed the vibration and shocks created by rough travel surfaces. The picture shows the front axle of a Deere tractor. The wheel hub is on the right side and the suspension is just to the right. A similar system will be on the other front wheel. In the lower middle of the picture is a silver part which is much like a shock absorber on a car or truck.

37. Tractor chasis suspension
More beneficial for the higher speeds
Front axle suspension – Deere
Front and rear axle suspension - Fastrac
Reduces potential for power hop
Improved performance with FWA tractor
Power hop occurs on four wheel drive and front wheel assist tractors where conditions sometime exist where the tractor bounces back and forth. A suspension system will reduce this problem and improve performance. Right photo is a picture of the tractor front end with suspension system and the wheels in place. Left photo appeared on the preceding slide.

38. Concluding remarks Guidance and auto-steer IVT/CVT Suspension Systems
Fuel saving
Automatic shift up-throttle back
Suspension Systems
Seat
Cab
Chassis
Guidance/auto-steer systems are becoming more available and the costs are becoming less. They reduce operator fatigue and allow for more hours of operation including hours of darkness. IVT/CVT provide an infinite number of speeds for better matching of tractor power with load and provides a fuel saving. They also reduce the need for the use of feet during operation. Active tractor seat provide better operator comfort and the suspension systems improve tractor performance.

39. QUESTIONS