公开(公告)号：US5249161A

公开(公告)日：1993-09-28

申请号：US934082

申请日：1992-08-21

申请人： Phillip K. Jones ,  David Malone

发明人： Phillip K. Jones ,  David Malone

IPC分类号： E21B47/18 ,  G05B19/4061

CPC分类号： E21B47/18 ,  E21B47/182 ,  G05B19/4061 ,  G05B2219/37622

摘要： Methods and apparatus for determining whether an encoder of a borehole tool is jammed are disclosed. The borehole tool has a motor with a drive shaft which is coupled to and drives an encoder, a position sensor coupled to the motor for sensing the position of the motor, and a microprocessor coupled to the position sensor and to the motor in a feedback loop, with the microprocessor controlling the movement of the motor based on the sensed position of the motor and the desired position of the motor. The method for determining jamming includes: determining, at a first plurality of times, positions of the motor from the position sensor; determining position errors of the motor from the positions of the motor and desired positions of the motor as determined by the microprocessor; and determining whether the encoder is jammed based on whether the position error exceeds a threshold value. In determining jamming, the microprocessor can also determine the rotational velocity of the motor, and account is taken of whether the motor velocity exceeds a threshold velocity at a time when the position error exceeds its threshold value.