LOAD STABILITY SYSTEM

• US 3,756,543 A
• Filed: 08/05/1971
• Issued: 09/04/1973
• Est. Priority Date: 08/05/1971
• Status: Expired due to Term

• Current Assignee: Donald W. Fowler, Sean J O'Connor
• Original Assignee: Donald W. Fowler, Sean J O'Connor
• Inventors: O'Connor, Sean J., Fowler, Donald W.
• Primary Examiner(s): Buchler, Milton
• Assistant Examiner(s): Kunin, Stephen G.
• Application Number:
  US05/169,197
• Time in Patent Office: 761 Days
• Field of Search: 244/17.13,77R,77DZ,137R
• US Class Current: 244/177
• CPC Class Codes: G05D 1/0858 specially adapted for vertical take-off of aircraft

Abstract

A heavy lift helicopter supporting a load suspended on a long cable is automatically controlled to minimize pendular motion of the load beneath the helicopter. The inner control loop of an automatic flight control system of a helicopter has an additional input which is the summation of a function of the rate of change of the angle between the cable and vertical, and the lag filtered rate of change of the angle, in both the lateral (roll) and longitudinal (pitch) directions of the aircraft. The sense of the rate of lag rate inputs is such as to cause the helicopter to move so as to counteract pendular motion of the load and support cable.

Claims

1. Aircraft control system apparatus for stabilizing, against pendular motion, a load suspended beneath the aircraft on a cable exhibiting pendular motion having a basic period including first intervals substantially characterized by relatively high velocity and relatively small angle with respect to the vertical, and including second intervals substantially characterized by relatively low velocity and relatively large angle with respect to the vertical, comprising:

means for sensing motion of said cable with respect to vertical and for generating a manifestation as a function of said motion; and

means including first means responsive to said manifestation to cause said aircraft to move in a direction the same as the motion of the load during a substantial portion of said first intervals and including second means also responsive to said manifestation to cause said aircraft to move in a direction opposite to the motion of the load during a substantial portion of said second intervals.

2. Apparatus according to claim 1 wherein said manifestation generating means comprises:

means responsive to changes in the position of said cable with respect to vertical to generate a rate signal indication of the rate of change of the angle of said cable with respect to vertical; and

means responsive to said rate signal to generate said manifestation as the difference between the lag of said rate and said rate.

3. A system for stablizing a load suspended beneath an aircraft having a plurality of control surfaces for controlling the attitude and motion thereof, and including a flight control system for providing at least partial control over said control surfaces, comprising:

a load support cable adapted to extend downwardly beneath said aircraft and to support a load thereon;

means responsive to changes in the position of said cable with respect to vertical to generate a rate signal indication of the rate of change of the angle of said cable with respect to vertical; and

means responsive to said rate signal indication to provide a signal manifestation input to said flight control system which is dependent upon said rate and an additional function of said rate in a manner to cause motion of said aircraft so as to counteract pendular motion of said load therebeneath.

4. A system according to claim 3 wherein said additional function is proportional to the lag of said rate.

5. The system according to claim 3 wherein said additional function is proportional to the washed out integral of said rate.

6. The system according to claim 3 wherein said additional function is provided by a lag filter having a transfer characteristic proportional to 1/(ts+1) where s is the LaPlacian operator and t is the time constant.