LOAD STABILITY SYSTEM

• US 3,833,189 A
• Filed: 01/04/1973
• Issued: 09/03/1974
• 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: Fowler, Donald W., O'Connor, Sean J.
• Primary Examiner(s): Blix, Trygve M.
• Assistant Examiner(s): Kelmachter, Barry L.
• Application Number:
  US05/321,061
• Time in Patent Office: 607 Days
• Field of Search: 244/17.13,137R,77R,77OZ,17.11
• US Class Current: 244/177
• CPC Class Codes: B64C 27/57 automatic or condition responsive, e.g. responsive to rotor speed, torque or thrust
• CPC Class Codes: B64D 1/22 Taking-up articles from earth's surface
• 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. In an aircraft having a load suspended 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, said aircraft having a plurality of control surfaces for controlling the attitude and motion thereof and a flight control system for providing at least partial control over said control surfaces, the method of stabilizing said load against pendular motion which comprises:

sensing the motion of said cable with respect to vertical and providing a signal manifestation of the rate of change of the angle of said cable with respect to vertical; and

providing, in response to said rate of change of angle signal manifestation, a control signal manifestation input to said control system to cause said control surfaces to move said aircraft in a direction the same as the motion of the load during a substantial portion of said first intervals and to move said aircraft in a direction opposite to the motion of the load during a substantial portion of said second intervals.

2. The method according to claim 1 wherein said step of providing a control signal manifestation includes the steps of:

generating, in response to said rate of change of angle signal manifestation, a signal manifestation indication of the lag of said rate of change of angle signal manifestation; and

providing to said control system a control signal manifestation which is the difference between the lag signal manifestation and the rate of change signal manifestation.

3. The method according to claim 1 wherein said step of providing a control signal manifestation comprises:

generating an angle lag signal manifestation which is proportional to 1/(ts +

     1) of said rate of change of angle signal manifestation, where s is the LaPlacian operator and t is the time constant; and

providing said control input manifestation as the difference between said angle lag signal manifestation and said rate of change of angle signal manifestation.