Navigation of helicopter with limited polar groundspeed commands

• US 6,059,226 A
• Filed: 04/29/1998
• Issued: 05/09/2000
• Est. Priority Date: 04/29/1998
• Status: Expired due to Term

• Current Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Original Assignee: Sikorsky Aircraft Corporation (Martin Marietta Corporation)
• Inventors: Walsh, David M., Cotton, Bryan S.
• Primary Examiner(s): Barefoot, Galen L.
• Application Number:
  US09/069,319
• Time in Patent Office: 741 Days
• Field of Search: 244/17.11, 244/17.13, 244/17.25, 244/194, 244/195, 244/175, 702/144, 701/7, 701/8, 701/10, 701/200, 701/201
• US Class Current: 244/17.13
• CPC Class Codes: G05D 1/0858 specially adapted for vertical take-off of aircraft

Abstract

The airspeed limiting performance envelope of a helicopter is converted to a groundspeed envelope by factoring-in the wind speed and direction. A groundspeed command for an unmanned helicopter is provided as a function of the range to the helicopter'"'"'s destination. The function may be calculated so as to provide a nominal groundspeed command equal to a nominal groundspeed command limit, or the function may be a fixed function to cause the aircraft to creep toward final approach. The cosine and sine of the desired relative flight direction of the aircraft, which is equal to the true bearing to the destination minus the true heading of the aircraft, are utilized to scale the groundspeed command into a longitudinal groundspeed command and a lateral groundspeed command. If one of the groundspeed commands is over a corresponding limit, the other groundspeed command is scaled back so that the vector addition of the two commands will cause flight in the desired direction. Exceedance of either a right or left groundspeed command, as well as saturation of the right or left cyclic pitch channel will cause the aircraft heading to be yawed into the direction of the limit exceedance or channel saturation.

Claims

1. Apparatus for providing a groundspeed envelope for a helicopter, comprising:

means providing a true wind direction signal indicative of the direction of wind in the environment of the helicopter;

means providing a true heading signal indicative of the true heading of the helicopter;

means providing a wind speed signal indicative of the speed of the wind in the environment of the helicopter; and

means for providing a relative wind direction signal as the difference between said true wind direction signal and said true heading signal, for providing a longitudinal wind speed signal as the wind speed signal multiplied by the cosine of said relative wind direction signal, for providing a lateral wind speed signal as the product of said wind speed signal and the sine of said relative wind direction signal, for providing a forward airspeed limit signal, an aft airspeed limit signal, a right airspeed limit signal, and a left airspeed limit signal, said limit signals being indicative of the airspeed safety envelope of the helicopter, for providing a forward groundspeed limit signal as a summation of said longitudinal wind speed signal and said forward airspeed limit signal, for providing an aft groundspeed limit signal as a summation of said longitudinal wind speed signal and said aft airspeed limit signal, for providing a right groundspeed limit signal as a summation of said lateral wind speed signal and said right airspeed limit signal, and for providing a left groundspeed limit signal as a summation of said lateral wind speed signal and said left airspeed limit signal.

2. Speed command generating apparatus for a helicopter, comprising:

means providing a range to destination signal indicative of the distance to a destination to be reached by said helicopter;

means providing a true bearing to destination signal indicative of the bearing of the aircraft to the destination;

means providing a true heading signal indicative of the true heading of the aircraft; and

means for providing a desired aircraft direction signal as the difference between said true bearing signal and said true heading signal, for providing a groundspeed command signal as a limited function of said range to destination signal, for providing a longitudinal groundspeed command signal in response to said limited groundspeed command signal times the cosine of said desired aircraft direction signal; and

for providing a lateral groundspeed command signal in response to said limited groundspeed command signal times the sine of said desired aircraft direction signal.

3. Speed command generating apparatus for a helicopter, comprising:

means providing a range to destination signal indicative of the distance to a destination to be reached by said helicopter;

means providing a forward groundspeed limit signal indicative of a forward groundspeed limit for the helicopter; and

means for providing a speed constant signal as a function of said forward groundspeed limit signal and for providing a groundspeed command signal as a limited function of the product of said speed constant signal and said range to destination signal.

4. Apparatus according to claim 3 wherein:

said last named means, in response to said range to destination signal indicating a predetermined short distance to the destination, providing said speed constant signal as a fixed speed constant instead of as a function of a forward speed limit.

5. A heading control apparatus for a helicopter having a yaw channel, comprising:

means for providing a heading input command signal indicative of a commanded heading for the aircraft; and

means for providing a heading rate signal indicative of a desired yaw rate command as a function of the difference between said heading input command signal and the time integral of said heading rate signal, for providing a right limit exceeded signal indicative of a right lateral groundspeed command exceeding a limit, for providing a left limit exceeded signal indicative of a left lateral groundspeed command exceeding a limit, for providing a rate signal indicative of a fixed right yaw rate command in response to the presence of said right limit exceeded signal, for providing said rate signal indicative of a fixed left yaw rate command in response to the presence of said left limit exceeded signal, for providing a rate heading signal as the time integral of said rate signal, and for selectively either providing a yaw rate command to said yaw channel equal to said rate signal and a heading command signal to said yaw channel equal to said rate heading signal in response to either said right limit exceeded signal or said left limit exceeded signal, and for otherwise providing said yaw rate command signal to said yaw channel in response to said heading rate signal, and providing said heading command signal to said yaw channel in response to said command heading signal.

6. Apparatus according to claim 5 wherein said means for providing a heading input command signal alternatively provides a signal indicative of heading into the wind in hover or heading to a destination in cruise.

7. An automatic flight control for a helicopter, comprising:

means providing a true wind direction signal indicative of the direction of wind in the environment of the helicopter;

means providing a true heading signal indicative of the true heading of the helicopter;

means providing a wind speed signal indicative of the speed of the wind in the environment of the helicopter;

means providing a range to destination signal indicative of the distance to a destination to be reached by said helicopter;

means providing a true bearing to destination signal indicative of the bearing of the aircraft to the destination;

means providing a heading input command signal indicative of a commanded heading for the aircraft; and

means for providing a relative wind direction signal as the difference between said true wind direction signal and said true heading signal, for providing a longitudinal wind speed signal as the wind speed signal multiplied by the cosine of said relative wind direction signal, for providing a lateral wind speed signal as the product of said wind speed signal and the sine of said relative wind direction signal, for providing a forward airspeed limit signal, an aft airspeed limit signal, a right airspeed limit signal, and a left airspeed limit signal, said limit signals being indicative of the airspeed safety envelope of the helicopter, for providing a forward groundspeed limit signal as a summation of said longitudinal wind speed signal and said forward airspeed limit signal, for providing an aft groundspeed limit signal as a summation of said longitudinal wind speed signal and said aft airspeed limit signal, for providing a right groundspeed limit signal as a summation of said lateral wind speed signal and said right airspeed limit signal, for providing a left groundspeed limit signal as a summation of said lateral wind speed signal and said left airspeed limit signal, for providing a desired aircraft direction signal as the difference between said true bearing signal and said true heading signal, for providing a speed constant signal as a function of said forward groundspeed limit signal, for providing a groundspeed command signal as a limited function of the product of said speed constant signal and said range to destination signal, for providing a longitudinal groundspeed command signal in response to said limited groundspeed command signal times the cosine of said desired aircraft direction signal, for providing a lateral groundspeed command signal in response to said limited groundspeed command signal times the sine of said desired aircraft direction signal, for providing a heading rate signal indicative of a desired yaw rate command as a function of the difference between said heading input command signal and the time integral of said heading rate signal, for providing a right limit exceeded signal indicative of a right lateral groundspeed command exceeding a limit, for providing a left limit exceeded signal indicative of a left lateral groundspeed command exceeding a limit, for providing a rate signal indicative of a fixed right yaw rate command in response to the presence of said right limit exceeded signal, for providing said rate signal indicative of a fixed left yaw rate command in response to the presence of said left limit exceeded signal, for providing a rate heading signal as the time integral of said rate signal, and for selectively either providing a yaw rate command to said yaw channel equal to said rate signal and a heading command signal to said yaw channel equal to said rate heading signal in response to either said right limit exceeded signal or said left limit exceeded signal, and for otherwise providing said yaw rate command signal to said yaw channel in response to said heading rate signal, and providing said heading command signal to said yaw channel in response to said command heading signal.

8. A method of providing a groundspeed envelope for a helicopter, comprising:

providing a true wind direction signal indicative of the direction of wind in the environment of the helicopter;

providing a true heading signal indicative of the true heading of the helicopter;

providing a wind speed signal indicative of the speed of the wind in the environment of the helicopter;

providing a relative wind direction signal as the difference between said true wind direction signal and said true heading signal;

providing a longitudinal wind speed signal as the wind speed signal multiplied by the cosine of said relative wind direction signal;

providing a lateral wind speed signal as the product of said wind speed signal and the sine of said relative wind direction signal;

providing a forward airspeed limit signal, an aft airspeed limit signal, a right airspeed limit signal, and a left airspeed limit signal, said limit signals being indicative of the airspeed safety envelope of the helicopter;

providing a forward groundspeed limit signal as a summation of said longitudinal wind speed signal and said forward airspeed limit signal;

providing an aft groundspeed limit signal as a summation of said longitudinal wind speed signal and said aft airspeed limit signal;

providing a right groundspeed limit signal as a summation of said lateral wind speed signal and said right airspeed limit signal; and

providing a left groundspeed limit signal as a summation of said lateral wind speed signal and said left airspeed limit signal.

9. A method of generating speed commands for a helicopter, comprising:

providing a range to destination signal indicative of the distance to a destination to be reached by said helicopter;

providing a true bearing to destination signal indicative of the bearing of the aircraft to the destination;

providing a true heading signal indicative of the true heading of the aircraft;

providing a desired aircraft direction signal as the difference between said true bearing signal and said true heading signal;

providing a groundspeed command signal as a limited function of said range to destination signal;

providing a longitudinal groundspeed command signal in response to said limited groundspeed command signal times the cosine of said desired aircraft direction signal; and

providing a lateral groundspeed command signal in response to said limited groundspeed command signal times the sine of said desired aircraft direction signal.

10. A method of controlling heading in a helicopter having a yaw channel, comprising:

providing a heading input command signal indicative of a commanded heading for the aircraft;

providing a heading rate signal indicative of a desired yaw rate command as a function of the difference between said heading input command signal and the time integral of said heading rate signal;

providing a right limit exceeded signal indicative of a right lateral groundspeed command exceeding a limit;

providing a left limit exceeded signal indicative of a left lateral groundspeed command exceeding a limit;

providing a rate signal indicative of a fixed right yaw rate command in response to the presence of said right limit exceeded signal;

providing said rate signal indicative of a fixed left yaw rate command in response to the presence of said left limit exceeded signal;

providing a rate heading signal as the time integral of said rate signal; and

selectively either providing a yaw rate command to said yaw channel equal to said rate signal and a heading command signal to said yaw channel equal to said rate heading signal in the presence of either said right limit exceeded signal or said left limit exceeded signal, or otherwise providing said yaw rate command signal to said yaw channel in response to said heading rate signal, and providing said heading command signal to said yaw channel in response to said command heading signal.

11. A method of generating a speed command for a helicopter, comprising:

providing a range to destination signal indicative of the distance to a destination to be reached by said helicopter;

providing a forward groundspeed limit signal indicative of a forward groundspeed limit for the helicopter;

providing a speed constant signal as a function of said forward groundspeed limit signal; and

providing a groundspeed command signal as a limited function of the product of said speed constant signal and said range to destination signal.

12. A method of controlling a helicopter, comprising:

providing a true wind direction signal indicative of the direction of wind in the environment of the helicopter;

providing a true heading signal indicative of the true heading of the helicopter;

providing a wind speed signal indicative of the speed of the wind in the environment of the helicopter;

providing a range to destination signal indicative of the distance to a destination to be reached by said helicopter;

providing a true bearing to destination signal indicative of the bearing of the aircraft to the destination;

providing a heading input command signal indicative of a commanded heading for the aircraft;

providing a relative wind direction signal as the difference between said true wind direction signal and said true heading signal;

providing a longitudinal wind speed signal as the wind speed signal multiplied by the cosine of said relative wind direction signal;

providing a lateral wind speed signal as the product of said wind speed signal and the sine of said relative wind direction signal;

providing a forward airspeed limit signal, an aft airspeed limit signal, a right airspeed limit signal, and a left airspeed limit signal indicative of the airspeed safety envelope of the helicopter;

providing a forward groundspeed limit signal as a summation of said longitudinal wind speed signal and said forward airspeed limit signal;

providing an aft groundspeed limit signal as a summation of said longitudinal wind speed signal and said aft airspeed limit signal;

providing a right groundspeed limit signal as a summation of said lateral wind speed signal and said right airspeed limit signal;

providing a left groundspeed limit signal as a summation of said lateral wind speed signal and said left airspeed limit signal;

providing a desired aircraft direction signal as the difference between said true bearing signal and said true heading signal;

providing a speed constant signal as a function of said forward groundspeed limit signal;

providing a groundspeed command signal as a limited function of the product of said speed constant signal and said range to destination signal;

providing a longitudinal groundspeed command signal in response to said limited groundspeed command signal times the cosine of said desired aircraft direction signal;

providing a lateral groundspeed command signal in response to said limited groundspeed command signal times the sine of said desired aircraft direction signal;

providing a heading rate signal indicative of a desired yaw rate command as a function of the difference between said heading input command signal and the time integral of said heading rate signal;

providing a right limit exceeded signal indicative of a right lateral groundspeed command exceeding a limit;

providing a left limit exceeded signal indicative of a left lateral groundspeed command exceeding a limit;

providing a rate signal indicative of a fixed right yaw rate command in response to the presence of said right limit exceeded signal;

providing said rate signal indicative of a fixed left yaw rate command in response to the presence of said left limit exceeded signal;

providing a rate heading signal as the time integral of said rate signal; and

selectively either providing a yaw rate command to said yaw channel equal to said rate signal and a heading command signal to said yaw channel equal to said rate heading signal in response to either said right limit exceeded signal or said left limit exceeded signal, and otherwise providing said yaw rate command signal to said yaw channel in response to said heading rate signal, and providing said heading command signal to said yaw channel in response to said command heading signal.