System and method to shift transmission in machines

1. A method for shifting a transmission in a machine, the method comprising:

detecting, by a controller, a request for a directional shift of the transmission;

determining, by the controller, a ground speed of the machine in response to the request;

overriding, by the controller, the request if the ground speed is above a ground speed threshold;

preparing, by the controller, the machine for the directional shift by:

limiting an output speed of a power source of the machine; and

issuing a command to a brake unit of the machine to reduce the ground speed of the machine; and

validating and raising, by the controller, the request to the transmission to execute the directional shift if the ground speed is below the ground speed threshold,

wherein the power source includes an internal combustion engine, and limiting the output speed of the power source includes:

detecting, by the controller, the output speed of the internal combustion engine;

comparing, by the controller, the output speed of the internal combustion engine to an engine speed threshold; and

reducing, by the controller, a supply of fuel into the internal combustion engine if the output speed of the internal combustion engine is above the engine speed threshold.

2. The method of claim 1 , wherein issuing the command includes:

determining a speed error signal by comparing and deducing a difference between an actual ground speed of the machine and a target ground speed of the machine;

scaling the speed error signal to respectively arrive at a proportionally scaled error signal and an integrally scaled error signal; and

summating the proportionally scaled error signal with the integrally scaled error signal to arrive at the command.

3. The method of claim 2 , wherein:

scaling the speed error signal to arrive at the integrally scaled error signal includes obtaining an integral of a product of the speed error signal and an integral gain associated with the speed error signal.

4. The method of claim 2 , wherein:

scaling the speed error signal to arrive at the proportionally scaled error signal includes obtaining a product of the speed error signal and a proportional gain associated with the speed error signal to arrive at a first value.

5. The method of claim 4 further comprising:

receiving, by the controller, data indicating an angle of inclination of the machine, wherein:

scaling the speed error signal to arrive at the proportionally scaled error signal includes obtaining a product of the speed error signal and a gain associated with the angle of inclination to arrive at a second value.

6. The method of claim 5 further comprising:

receiving, by the controller, data indicating a weight of a payload carried by the machine, wherein:

scaling the speed error signal to arrive at the proportionally scaled error signal includes obtaining a product of the speed error signal and a gain associated with the weight of the payload to arrive at a third value.

7. The method of claim 6 , wherein scaling the speed error signal to arrive at the proportionally scaled error signal includes adding together the first value, the second value, and the third value.

8. A machine, comprising:

a power source to generate power;

a transmission operably coupled to the power source to receive power from the power source and transfer the power to one or more traction devices of the machine to facilitate machine motion;

a brake unit to apply braking force against the one or more traction devices to retard machine motion;

a control system for shifting the transmission, the control system including:

a controller configured to:

detect a request for a directional shift of the transmission;

determine a ground speed of the machine in response to the request;

override the request if the ground speed is above a ground speed threshold;

prepare the machine for the directional shift by:

limiting an output speed of the power source; and

issuing a command to the brake unit to reduce the ground speed of the machine; and

validate and raise the request to the transmission to execute the directional shift if the ground speed is below the ground speed threshold,

wherein the power source includes an internal combustion engine, and for limiting the output speed of the power source the controller is configured to:

detect the output speed of the internal combustion engine;

compare the output speed of the internal combustion engine to an engine speed threshold; and

reduce a supply of fuel into the internal combustion engine if the output speed of the internal combustion engine is above the engine speed threshold.

9. The machine of claim 8 , wherein to issue the command, the controller is configured to:

determine a speed error signal by comparing and deducing a difference between an actual ground speed of the machine and a target ground speed of the machine;

scale the speed error signal to respectively arrive at a proportionally scaled error signal and an integrally scaled error signal; and

summate the proportionally scaled error signal with the integrally scaled error signal to arrive at the command.

10. The machine of claim 9 , wherein to scale the speed error signal to arrive at the integrally scaled error signal, the controller is configured to obtain an integral of a product of the speed error signal and an integral gain associated with the speed error signal.

11. The machine of claim 9 , wherein to scale the speed error signal to arrive at the proportionally scaled error signal, the controller is configured to obtain a product of the speed error signal and a proportional gain associated with the speed error signal to arrive at a first value.

12. The machine of claim 11 , wherein the controller is configured to receive data indicating an angle of inclination of the machine, and wherein to scale the speed error signal to arrive at the proportionally scaled error signal, the controller is configured to obtain a product of the speed error signal and a gain associated with the angle of inclination to arrive at a second value.

13. The machine of claim 12 , wherein the controller is configured to receive data indicating a weight of a payload carried by the machine, and wherein to scale the speed error signal to arrive at the proportionally scaled error signal, the controller is configured to obtain a product of the speed error signal and a gain associated with the weight of the payload to arrive at a third value.

14. The machine of claim 13 , wherein to scale the speed error signal to arrive at the proportionally scaled error signal, the controller is configured to add together the first value, the second value, and the third value.

15. A control system for shifting a transmission in a machine, the control system comprising:

a controller configured to:

detect a request for a directional shift of the transmission;

determine a ground speed of the machine in response to the request;

override the request if the ground speed is above a ground speed threshold;

prepare the machine for the directional shift by:

limiting an output speed of a power source of the machine; and

issuing a command to a brake unit of the machine to reduce the ground speed of the machine; and

validate and raise the request to the transmission to execute the directional shift if the ground speed is below the ground speed threshold,

wherein to issue the command, the controller is configured to:

determine a speed error signal by comparing and deducing a difference between an actual ground speed of the machine and a target ground speed of the machine;

scale the speed error signal to respectively arrive at a proportionally scaled error signal and an integrally scaled error signal; and

summate the proportionally scaled error signal with the integrally scaled error signal to arrive at the command.

16. The control system of claim 15 , wherein the power source includes an internal combustion engine, and for limiting the output speed of the power source the controller is configured to:

detect the output speed of the internal combustion engine;

compare the output speed of the internal combustion engine to an engine speed threshold; and

reduce a supply of fuel into the internal combustion engine if the output speed of the internal combustion engine is above the engine speed threshold.

17. The control system of claim 15 , wherein the controller is configured to:

receive data indicating an angle of inclination of the machine;

receive data indicating a weight of a payload carried by the machine, and wherein to scale the speed error signal to arrive at the proportionally scaled error signal, the controller is configured to:

obtain a product of the speed error signal and a proportional gain associated with the speed error signal to arrive at a first value;

obtain a product of the speed error signal and a gain associated with the angle of inclination of the machine to arrive at a second value;

obtain a product of the speed error signal and a gain associated with the weight of the payload carried by the machine to arrive at a third value; and

add together the first value, the second value, and the third value.