Anti-rollover for harvesters with electronic steering

1. A steering system for a machine, the steering system comprising:

a steer-by-wire system configured to provide rear wheel steering, the steer-by-wire system comprising:

a human-machine-interface (HMI) configured to provide a force feedback to the HMI that influences the HMI to a center position;

plural sensors; and

one or more controllers configured by executable code to receive input from one or more of the plural sensors and reduce a risk of rollover by:

causing rear wheels of the machine to maintain or return to straight forward travel in conjunction with the force feedback;

limiting a steering angle of the machine, beyond which a rollover condition occurs, based on computation of a rollover equation with parameters corresponding to the input and a machine geometry; and

providing a steering command based on a roll angle of the machine exceeding a threshold rollover angle based on input from the plural sensors,

wherein the one or more controllers are configured to provide the steering command by applying a control equation to a non-linear set of curves that are proportional to machine speed to generate a dynamic steering input, the dynamic steering input comprising a counter-steer component provided to a steering angle set-point calculation.

2. The steering system of claim 1 , wherein the plural sensors include an inertial sensor, and wherein the one or more controllers are further configured to provide a steering command based on a roll angle of the machine exceeding a threshold rollover angle based on input from the inertial sensor.

3. The steering system of claim 1 , wherein the one or more controllers are configured to cause the rear wheels to maintain or return to straight forward travel by:

receiving a steering angle command from the HMI based on operator input;

generating a steering angle reference value based on the steering angle command; and

providing a final steering angle set-point constrained by a maximum steering angle corresponding to mechanical function of the steering system.

4. The steering system of claim 1 , wherein the counter-steer component corresponds to a single step torque response.

5. The steering system of claim 1 , wherein the control equation comprises a derivative with temporary lag mathematical equation.

6. The steering system of claim 1 , wherein the HMI comprises a steering control for the machine that is configured to be directly manipulated by an operator.

7. The steering system of claim 1 , wherein the force feedback is experienced by an operator in contact with the HMI based on cooperation between the HMI and a biasing device and a torque set-point received by the one or more controllers.

8. The steering system of claim 7 , wherein the force feedback increases force as a function of speed of the machine.

9. The steering system of claim 7 , wherein the biasing device comprises a spring, a resilient device, or an electromagnetic motor.

10. A steering system for a machine, the steering system comprising:

a steer-by-wire system configured to provide rear wheel steering, the steer-by-wire system comprising:

a human-machine-interface (HMI) configured to provide a force feedback to the HMI that influences the HMI to a center position;

plural sensors; and

one or more controllers configured by executable code to receive input from one or more of the plural sensors and reduce a risk of rollover by:

causing rear wheels of the machine to maintain or return to straight forward travel in conjunction with the force feedback; and

limiting a steering angle of the machine, beyond which a rollover condition occurs, based on computation of a rollover equation with parameters corresponding to the input and a machine geometry,

wherein the one or more controllers are configured to limit the steering angle of the machine based on—

computing a square value of ground speed, and

computing a maximum allowed steering angle according to the rollover equation based on the square value of the ground speed, a length of a rear axle of the machine, and a height of center of mass of the machine, the maximum allowed steering angle corresponding to a maximum radius at a given speed without having a rollover condition.

11. The steering system of claim 10 , wherein the one or more controllers are configured to limit the maximum allowed steering angle to within boundaries of a maximum mechanical limit of steering.

12. The steering system of claim 10 , wherein the rollover equation consists of r=2*(h/(d*g))*v.sup.2, where r equals a rollover curvature radius from the center of mass of the machine, h equals the height of the machine at the center of mass, d equals the rear axle length or distance, g equals earth gravity, and v equals velocity or the ground speed of the machine.

13. The steering system of claim 10 , wherein the one or more controllers are configured to limit a steering angle reference value corresponding to a steering command received from the HMI using the maximum allowed steering angle.

14. A non-transitory, computer readable storage medium comprising instructions that, when executed by one or more processors, causes the one or more processors to reduce a risk of rollover in a rear wheel steering machine by:

receiving input from one or more sensors;

biasing a human-machine-interface (HMI) to provide a force feedback to influence the HMI to a center position;

causing rear wheels of the machine to maintain or return to straight forward travel in conjunction with the force feedback;

limiting a steering angle of the machine, beyond which a rollover condition occurs, based on computation of a rollover equation with parameters corresponding to the input and a machine geometry; and

providing a steering command based on a roll angle of the machine exceeding a threshold rollover angle, wherein providing the steering command comprises applying a control equation to a non-linear set of curves that are proportional to machine speed to generate a dynamic steering input, the dynamic steering input comprising a counter-steer component provided to a steering angle set-point calculation to cause a counter-steer to a prior steering movement of the machine.

15. A rear wheel steering method for a machine, the steering method comprising:

receiving input from one or more sensors; and

reducing a risk of machine rollover by:

biasing a human-machine-interface (HMI) to provide a force feedback to influence the HMI to a center position;

causing rear wheels of the machine to maintain or return to straight forward travel in conjunction with the force feedback;

limiting a steering angle of the machine, beyond which a rollover condition occurs, based on computation of a rollover equation with parameters corresponding to the input and a machine geometry; and

providing a steering command based on a roll angle of the machine exceeding a threshold rollover angle, wherein providing the steering command comprises applying a control equation to a non-linear set of curves that are proportional to machine speed to generate a dynamic steering input, the dynamic steering input comprising a counter-steer component provided to a steering angle set-point calculation to cause a counter-steer to a prior steering movement of the machine.

16. The steering method of claim 15 , wherein the causing further comprises:

receiving a steering angle command;

generating a steering angle reference value based on the steering angle command; and

providing a final steering angle set-point constrained by a maximum steering angle corresponding to mechanical function of a steering system.

17. A rear wheel steering method for a machine, the steering method comprising:

receiving input from one or more sensors; and

reducing a risk of machine rollover by:

biasing a human-machine-interface (HMI) to provide a force feedback to influence the HMI to a center position;

causing rear wheels of the machine to maintain or return to straight forward travel in conjunction with the force feedback; and

limiting a steering angle of the machine, beyond which a rollover condition occurs, based on computation of a rollover equation with parameters corresponding to the input and a machine geometry,

wherein the step of limiting the steering angle of the machine includes the steps of—

computing a square value of ground speed of the machine; and

computing a maximum allowed steering angle according to the rollover equation based on the square value of the ground speed, a length of a rear axle of the machine, and a height at center of mass of the machine, the maximum allowed steering angle corresponding to a maximum radius at a given speed without having a rollover condition.