Patent Application
20240116569
The present invention relates to grass mowing machines, and more specifically to a radial differential speed control system for grass mowing machines such as triplex greensmowers.
Grass mowing machines used to mow golf courses, parks, and athletic fields where a high quality of cut is desired, may include three or more reel cutting units. For example, triplex greensmowers have two forward reel cutting units followed by a center or rear reel cutting unit positioned under the vehicle frame and the operator station. Reel cutting units have front and rear rollers, spiral cutting blades rotating in close proximity to a bedknife, and may have a removable grass catcher mounted in front of the cutting unit. For example, a reel cutting unit may have 8 spiral cutting blades.
Triplex greensmowers have a pair of front wheels and a steerable rear wheel. Electric traction drive systems on triplex greensmowers enable differential speed control for each of the front wheels. However, if electric traction drive systems have differential control but do not provide vehicle speed reduction when turning, the driver may experience high centrifugal forces, and possible turf damage may result.
There is a need for a radial differential speed control system that reduces ground speed of a triplex greensmower when turning, minimizes centrifugal forces, and reduces turf damage.
A radial differential speed control system includes a controller that provides differential speed commands to electric motors for a left front drive wheel and a right front drive wheel based on a sensor input for a turning angle of a steerable rear wheel. The controller provides commands that reduce speed at a reference point on a centerline of the grass mowing machine that is rearward of an axis of the left and right front drive wheels and toward the steerable rear wheel.
In one embodiment, radial differential speed control system 100 may include a sensor input to controller 105 for the angle ϕ1 of steerable rear wheel 110. The controller may use angle ϕ1 to determine the location of point 0, the instantaneous turn center of the triplex greensmower or other grass mowing machine. In
In one embodiment, radial differential speed control system 100 may include a pedal input to the controller for desired ground speed Vveh at reference point VEH. Reference point VEH may be located anywhere on the centerline of a triplex greensmower or other grass mowing machine, rearward of front wheel axis FA. To minimize centrifugal force and improve operator feel, reference point VEH may be located near the operator seat. For example, the grass mowing machine may include a display or input device to the controller, which the operator may use to enter the desired location of VEH, or move the location forward or rearward.
In one embodiment, the radial differential speed control system may include a controller that calculates the ground speed VFA at the centerline of the front drive wheel axis, based on the desired ground speed Vveh at reference point VEH, and angle ϕ2 from VEH to point 0. To calculate the ground speed VFA at the centerline of the front drive wheel axis, the controller may use the equation VFA=cos(ϕ2)*Vveh.
In one embodiment, the radial differential speed control system may include a controller that adjusts speed commands ωL and ωR to the electric motors for the left and right front drive wheels to reduce the ground speed of the grass mowing machine when turning. The speed commands may be a function of the turning angle ϕ1 of steerable rear wheel 110, the speed VFA at the front axle, and the location of reference point VEH relative to the front axle. To provide more aggressive speed reduction and improve operator feel during turns, the operator may move VEH d further rearward toward the steerable rear wheel, increasing the distance VSL from front drive wheel axis FA to reference point VEH.
In one embodiment, the radial differential speed control system may include a controller that may store and use fixed dimensions of the triplex greensmower or other grass mowing machine. For example, the calculations may include CRL which is one half of the front track width of the triplex greensmower (and the distance from point FA to either front drive wheel); and CML, the distance from the front drive wheel axis to the rear steerable wheel axis.
In one embodiment, the radial differential speed control system may include a controller that calculates the distance from each front drive wheel to point 0, the instantaneous turn center. The controller first may calculate R0, the distance from the mower centerline to point 0, using the equation R0=CML/tan(ϕ1). The controller then may calculate Rleft, the distance from the left front wheel to point 0, using the equation Rleft=R0+CRL; and Rright, the distance from the right front wheel to point 0, using the equation Rright=R0−CRL. Optionally, the controller may calculate Rrear, the distance from the center or rear steerable wheel to point 0, using the equation Rrear=CML/sin(ϕ1).
In one embodiment, the radial differential speed control system may include a controller that calculates and provides differential speed commands ωL and ωR to the left and right front wheel motors when turning. The controller may use the equation ωL=(Rleft/R0)*VFA for the speed command to the left front wheel motor, and the equation ωR=(Rright/R0)*VFA for the speed command to the right wheel motor when turning. Optionally, the controller may use the equation ωC=(Rrear/R0)*VFA for the speed command to the center or rear wheel motor when the grass mowing machine is turning. The differential speed commands may reduce speed of the grass mowing machine to improve operator feel and reduce turf damage when turning.
Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.
