Guidewire controls for a material handling vehicle

• US 5,778,327 A
• Filed: 11/12/1996
• Issued: 07/07/1998
• Est. Priority Date: 11/10/1993
• Status: Expired due to Term

• Current Assignee: The Raymond Corporation (Toyota Motor Corporation)
• Original Assignee: The Raymond Corporation (Toyota Motor Corporation)
• Inventors: Day, Richard M., Simmons, James M., Hellmann, Christopher J.
• Primary Examiner(s): Chin, Gary
• Application Number:
  US08/747,244
• Time in Patent Office: 602 Days
• Field of Search: 364/424.27, 364/424.28, 364/424.32, 318/580, 318/581, 318/587, 180/167, 180/168, 180/169, 701/23, 701/24, 701/27
• US Class Current: 701/23
• CPC Class Codes: B62D 1/28 non-mechanical , e.g. following a line or other known markers
• CPC Class Codes: G05D 1/0061 for transition from automatic pilot to manual pilot and vice versa
• CPC Class Codes: G05D 1/0221 involving a learning process
• CPC Class Codes: G05D 1/0265 using buried wires

Abstract

The present invention features a universal, manned, material handling vehicle. The material handling vehicle is capable of operating in a manned mode, a wire guidance mode, and a rail guidance mode. This manned material handling vehicle contains a steering management control system having a logic program which allows the vehicle to adapt itself to different wire control systems. That is, particular parameters, frequency and amplitude of the underlying wire guidance system can be determined. In this manner, the manned vehicle is universally adaptive to a wide variety of wire guidance systems. When in manned operation mode, should the vehicle receive a wire guidance signal, the system controller will be duly informed. When in wire guidance operation mode, should the vehicle lose or fail to receive a clear wire guidance signal appropriate to guide on, it will automatically revert to the manned operation mode. The steering management control system also monitors the weight and height of the vehicle'"'"'s load. This steering management control system receives signals from the steering tiller, as well as from the guidewire embedded in the floor of the material storage facility.

Claims

1. A method to be used with a material handling vehicle that is operative in an automatic wire guidance mode, the vehicle used with a plurality of automatic wire guidance systems, each system transmitting guidance signals having a frequency and amplitude characteristic of the system, the guidance signals used to guide the vehicle, the vehicle including a steering control means and a signal sensor, the control means including a frequency filter and a gain amplifier, the method for automatically setting the filter frequency and amplifier gain so that the steering control means is responsive to guidance signals from one of said guidance systems, said one of the guidance systems being a system with which the vehicle is to be used, the method comprising the steps of:

a) sensing the guidance signal corresponding to the one of the guidance systems;

b) processing the sensed signal to ascertain the characteristic frequency of the guidance signal and determine the amplitude gain required to alter the guidance signals for use by the control means; and

c) setting the filter frequency and the amplifier gain so that the steering control means is responsive to signals having substantially the characteristic amplitude and frequency of the guidance signals.

2. The method of claim 1 wherein the guidance system includes a guide wire and the step of sensing includes the step of generating feedback signals indicating the position of the vehicle with respect to the guide wire wherein the feedback signals also comprise information indicating the amplitude and frequency of the guidance signal.

3. The method of claim 1 wherein the step of processing includes the step of monitoring the feedback signals at each frequency within a range of possible guidance signal frequencies to identify the guidance signal frequency, the guidance signal frequency being the frequency at which the sensed signal is the strongest.

4. The method of claim 1 wherein the vehicle is also operative in a manual mode and the method further includes the step of, prior to the step of sensing, in the manual mode, moving the vehicle into a position within a receiving range of said one of the guidance systems.

5. An apparatus to be used with a material handling vehicle that is operative in an automatic wire guidance mode, the vehicle used with a plurality of automatic wire guidance systems, each system transmitting guidance signals having a frequency and amplitude characteristic of the system, the guidance signals used to guide the vehicle, the vehicle including a steering control means, the steering control means including a frequency filter and a gain amplifier, the apparatus for automatically setting the filter frequency and the amplifier gain so that the steering control means is responsive to guidance signals from one of said guidance systems, said one of the guidance systems being a system with which the vehicle is to be used, the apparatus comprising:

(a) a sensor for sensing the guidance signal corresponding to the one of the guidance systems;

(b) a processor for processing the sensed signal to ascertain the characteristic frequency of the guidance signals and determine the amplitude gain required to alter the guidance signals for use by the control means; and

c) means for setting the filter frequency and the amplifier gain so that the steering control means is responsive to signals having the characteristic amplitude and frequency of the guidance signals.

6. The apparatus of claim 5 wherein said one of the guidance systems includes a guidewire and the sensor generates feedback signals indicating the position of the vehicle with respect to the guidewire wherein the feedback signals also comprise information indicating the amplitude and frequency of the guidance signal.

7. The apparatus of claim 5 wherein the processor includes a monitor for monitoring the sensed signal at each frequency within a range of possible guidance signal frequencies to identify the guidance signal frequency, the guidance signal frequency being the frequency at which the sensed signal is the strongest.

8. The apparatus of claim 7 wherein said steering control means includes a variable gain amplitude amplifier and the means for setting changes the amplifier gain so that an amplified guidance signal has an amplitude within a steering control means range and the means for setting calibrates said steering control means to be responsive to signals at substantially the guidance signal frequency.

9. A method to be used with a material handling vehicle that is operative in an automatic wire guidance mode, the vehicle used with an automatic wire guidance system, the system transmitting a guidance signal used to guide the vehicle, the vehicle including a steering control means and at least first and second signal sensors to sense the guidance signal, the method for minimizing the effects of noise on the position of the vehicle with respect to the guidance wire, the method comprising the steps of:

a) sensing the guidance signal using the first and the second signal sensors to provide first and second sensed signals;

subtracting the first signal from the second signal to generate a differenced output indicative of the position of the guidance wire with respect to the sensors;

c) limiting the maximum rate of change of the differenced output so as to minimize the effects of noise on the position of the vehicle with respect to the guidance wire; and

d) using the limited differenced output to adjust the position of the vehicle.

10. The method of claim 9 wherein the vehicle is operative in either the automatic wire guidance mode or a manual mode, the vehicle equipped with a mechanism for locking onto the guidewire, the method further including the steps of, when the vehicle is in the manual mode and switching over to the automatic wire guidance mode, setting the maximum rate of change to a first value while the mechanism is acquiring the guidance wire and setting the maximum rate of change to a second value after the mechanism has acquired the wires, wherein the first value is higher than the second value.