Constant tension cable reel drive

A control system for use with a vehicle mounted cable reel, a hydraulic motor for driving said cable reel, a source of hydraulic fluid under pressure for driving said motor, and said control system modulating the fluid flow from said source to said motor comprising;

• flow control means responsive to the fluid pressure differential across said motor which represents a torque feedback signal, electrohydraulic transducer means providing an input command signal to said flow control means, basic command means providing a basic signal for controlling said transducer means, speed sensing means responsive to the rotation of said cable reel to provide a speed signal proportional to cable reel rpm, transient condition command means receiving said speed signal and differentiating said speed signal to provide an acceleration signal, said acceleration signal being further provided to said transducer means to modify said basic signal in response to cable reel deceleration and acceleration to form said command signal, said flow control means responding to said command signal, said flow control means responding to said command signal to drive said motor in a manner which reaches equilibrium between said torque feedback signal and said command signal, and wherein said source of fluid power to said hydraulic motor consists of a variable displacement pump driven at constant rpm, said pump having servo control means for varying the displacement thereof, and said flow control means consists of a variable pressure control valve modulating fluid flow to said servo control means, said variable pressure control valve having a valve spool movable in response to said torque feedback signal provided by connection to fluid lines interconnecting said variable displacement pump and said fluid motor, said valve speed also being movable in response to a pressure differential generated by said electrohydraulic transducer means.

A control system for use with a vehicle mounted cable reel having a drive mechanism, said control system controlling the drive torque output of said mechanism to a cable reel wherein said cable reel has a pay-in direction of rotation and a pay-out direction of rotation, said control system comprising;

• basic command means providing a basic command signal for controlling said drive mechanism, said basic command means including direction detector means responsive to the rotation of said cable reel to provide said basic command signal which is greater in the pay-in direction of rotation of said cable reel than in the pay-out direction of rotation of said cable reel, and wherein said basic command means further includes diameter sensing means for determining the instantaneous diameter of the cable on said cable reel to modify said basic command signal in a decreasing direction as cable is unwound from said cable reel,
• speed sensing means responsive to the rotation of said cable reel to provide a speed signal proportional to cable reel rpm, transient condition command means responsive to the output of said speed sensing means to provide a transient condition signal for addition to said basic command signal, and
• summing means for receiving both said basic command signal and said transient condition signal and having an output signal provided to said drive mechanism whereby said basic command signal is modified by said transient condition signal.

A control system for use with a vehicle mounted cable reel having a drive mechanism, said control system controlling the drive torque output of said mechanism to a cable reel capable of rotation in a pay-in direction and in an opposite pay-out direction, said control system comprising;

• command means providing a command signal for controlling said drive mechanism, said command means including direction detector means responsive to the rotation of said cable reel to provide a pay-in and pay-out signal wherein said pay-in signal is greater than said pay-out signal to make up for reversal of cable friction between the pay-in direction of rotation and the pay-out direction of rotation, said pay-in and said pay-out signals being supplied to said drive mechanism for controlling the operation thereof, said command means further including feedback responsive means sensing the drive torque applied by said drive mechanism to said cable reel to provide a torque feedback signal for application to said drive mechanism, said command signal controlling said drive mechanism to maintain equilibrium with said torque feedback signal, and wherein said control system further includes diameter sensing means for determining the instantaneous diameter of the cable on said cable reel to modify said pay-in signal in an increasing direction as cable is wound on said cable reel and modify said pay-out signal in a decreasing direction as cable is unwound from said cable reel.

A control system for use with a vehicle mounted cable reel having a drive mechanism, said control system controlling the drive torque output of said mechanism to a cable reel capable of rotation in a pay-in direction and in an opposite pay-out direction, said control system comprising;

• command means providing a command signal for controlling said drive mechanism, said command means including direction detector means responsive to the rotation of said cable reel to provide a pay-in and a pay-out signal wherein said pay-in signal is greater than said pay-out signal to make up for reversal of cable reel friction between the pay-in direction of rotation and the pay-out direction of rotation, said pay-in and said pay-out signals being supplied to said drive mechanism for controlling the operation thereof, said command means further including feedback responsive means sensing the drive torque applied by said drive mechanism to said cable reel to provide a torque feedback signal for application to said drive mechanism, said command signal controlling said drive mechanism to maintain equilibrium with said torque feedback signal, and further including transient command means comprising speed sensing means responsive to the rotation of said cable reel to provide a speed signal proportional to cable reel rpm, said speed signal means providing an input for said direction detector means.

A control system for use with a vehicle mounted cable reel, a hydrostatic transmission consisting of a variable displacement pump driven at constant speed and connected to a hydraulic motor driving said cable reel, said variable displacement pump being of the axial piston type and having a movable swash plate for varying the displacement of said pump, servo control means for positioning said swash plate, and hydraulic valve means for controlling fluid flow to said servo control means, said control system comprising;

• torque feedback means measuring the pressure differential across said motor to apply a torque feedback signal to said hydraulic valve, an electrohydraulic transducer means providing a hydraulic signal to said hydraulic valve, basic command means providing a basic command signal to said electrohydraulic transducer means and consisting of cable reel diameter sensing means which increases said basic command signal upon an increase in amount of cable wound on said cable reel and cable reel rotational direction sensing means which increases the basic command signal when said cable reel is rotated in a direction to wind cable on said cable reel and decreases said basic command signal when said cable reel is rotated in a direction which reduces the amount of cable wound on said cable reel, transient condition command means including speed sensing means responsive to the rotation of said cable reel to provide a speed signal proportional to cable reel rpm and differentiating means for converting said speed signal into an acceleration signal, and means applying said acceleration signal to said electrohydraulic transducer means to modify the basic command signal upon a change of velocity of said cable reel.