Electronic tractor guidance system
First Claim
1. An automatic guidance system for controlling the direction of travel of a tractor to follow a guide path by generating a steering control signal to control the steering direction of the tractor, the system comprising:
- (a) a direction sensor connected to the tractor, for generating a path direction signal indicative of the direction of the path relative to the direction of travel of the tractor;
(b) a tractor steering means responsive to the steering control signal, for controlling the steering direction of the tractor;
(c) a tractor steering sensor connected to said steering means, for generating a steering direction of the tractor; and
(d) a control means responsive to said sensors, for generating the steering control signal, the steering control signal having a predetermined period with a variable duty cycle defined by an uninterrupted sequence of alternate time intervals of right and left turn steering corrections where the total time for each consecutive pair of right and left turn steering corrections is equal to the period of the steering control signal and where equal time intervals for the right and left turn steering corrections represents a 50% duty cycle so that the steering direction of the tractor is effected when the duty cycle of the steering signal deviates from the 50% duty cycle, said control means generating a variable amplitude convergence frequency signal where the amplitude of the convergence frequency signal determines the steering correction sensitivity of the guidance system to errors between the direction of the guide path and the direction of travel of the tractor by varying the rate of convergence of the steering direction to the direction of the path.
4 Assignments
0 Petitions
Accused Products
Abstract
An automatic tractor guidance system for controlling the steering of a tractor to follow a previously plowed furrow is disclosed. A furrow follower is provided with a sensor for sensing the direction of the path relative to the direction of travel of the tractor. The steering direction of the tractor is likewise sensed. The two sensor signals are combined and compared to a convergence frequency signal to produce a digital control signal. Each logic state of the control signal effects a turn in the steering of the tractor, right then left. If the duty cycle of the control signal is 50%, no net turn either right or left is effected. However, when the duty cycle deviates from 50%, a net rotation in one direction or the other will occur depending on which logic state of the digital signal occurs for a longer portion of each cycle of the control signal. Also provided is an offset adjustment to adjust the steering direction of the tractor to compensate for forces acting on the tractor which tend to change the direction of travel of the tractor without an accompanying steering control change.
34 Citations
15 Claims
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1. An automatic guidance system for controlling the direction of travel of a tractor to follow a guide path by generating a steering control signal to control the steering direction of the tractor, the system comprising:
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(a) a direction sensor connected to the tractor, for generating a path direction signal indicative of the direction of the path relative to the direction of travel of the tractor; (b) a tractor steering means responsive to the steering control signal, for controlling the steering direction of the tractor; (c) a tractor steering sensor connected to said steering means, for generating a steering direction of the tractor; and (d) a control means responsive to said sensors, for generating the steering control signal, the steering control signal having a predetermined period with a variable duty cycle defined by an uninterrupted sequence of alternate time intervals of right and left turn steering corrections where the total time for each consecutive pair of right and left turn steering corrections is equal to the period of the steering control signal and where equal time intervals for the right and left turn steering corrections represents a 50% duty cycle so that the steering direction of the tractor is effected when the duty cycle of the steering signal deviates from the 50% duty cycle, said control means generating a variable amplitude convergence frequency signal where the amplitude of the convergence frequency signal determines the steering correction sensitivity of the guidance system to errors between the direction of the guide path and the direction of travel of the tractor by varying the rate of convergence of the steering direction to the direction of the path. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. In an automatic tractor guidance system for steering a tractor to follow a guide path, the tractor including,
(a) a steering means including a steering wheel for steering the tractor, (b) sensors for sensing and generating signals of the travel direction of the tractor relative to the guide path, and of the steering direction of the tractor, and (c) means for combining the sensor outputs to obtain a steering error signal whose magnitude and polarity respectively represents the amount of steering correction and steering correction direction required to bring the travel direction of the tractor back to the direction of a guide path, an improvement comprising: a means responsive to said steering error signal for generating a steering control signal for controlling the steering of the tractor through an uninterrupted sequence of steering turn corrections whereby the amount of steering correction and the direction of the steering correction direction of the tractor are controlled by the steering control signal as a function of time, said means generating a variable amplitude convergence frequency signal whose amplitude determines the steering correction sensitivity of the guidance system by enabling the rate of convergence of the direction of travel of the tractor to follow the guide path to be controlled at a given value of the steering error signal. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method of controlling a vehicle having a steering system including a steering wheel to follow a guide path comprising the steps of:
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(a) sensing the steering direction of travel of the vehicle; (b) sensing the direction of the guide path relative to the direction of travel of the vehicle; (c) generating a steering error signal from the sensed direction of the guide path and the steering direction of the tractor, the steering error signal having, (i) a magnitude representative of the amount of steering correction needed to steer the vehicle to follow the guide path, and (ii) a polarity representative of the steering direction for the steering correction; (d) generating a variable amplitude convergence frequency signal having a fixed time period; (e) varying the amplitude of the convergence frequency signal to determine the steering correction sensitivity of the steering system for a given value of the steering error signal; and (f) comparing the steering error signal to the convergence frequency signal to obtain a steering control signal for controlling the steering of the vehicle, the steering control signal having an uninterrupted sequence of alternate steering correction states in each period of the convergence frequency signal and a duty cycle defined by the ratio of the time for each state during each period where equal time intervals for the states during a period represents a 50% duty cycle, and where the steering direction of the vehicle is effected when the duty cycle deviates from 50% thereby controlling the steering of the vehicle as a function of time. - View Dependent Claims (15)
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Specification