Constant pull winch controls

A constant load winch comprising:

• a rotatable winch drum;
• a winch cable that can be wound about and unwound from an outer surface of the winch drum, relative to an axis of rotation of the winch drum;
• an electric winch motor that drives rotation of the winch drum;
• and a constant load winch control system including a sensor that senses a number of layers of winch cable wound about the winch drum and a control system configured to output a control signal to the electric winch motor to control the electric winch motor to achieve a constant pulling force on the winch cable based on the number of layers sensed by the sensor and turn off the electric winch motor when an electrical current of the electric winch motor is greater than a threshold current for the determined number of layers, where for each different number of layers wound around the winch drum, there is a different threshold current for turning off the electric winch motor.

A method of operating a winch system to achieve a constant pulling force comprising the steps of, via a winch control system:

• setting a predefined constant pulling force for the winch system;
• determining a distance from a center axis of rotation of a winch drum of the winch system to an outer edge of a top layer of a winch cable wound around the winch drum;
• applying power to a winch motor of the winch system to rotate the winch drum and achieve the predefined constant pulling force;
• monitoring the distance from the center axis of rotation to the top layer of winch cable;
• determining whether a change is detected in the distance from the center axis of rotation to the top layer of winch cable;
• when the distance from the center axis of rotation to the top layer of winch cable changes, adjusting the power applied to the winch motor to maintain the predefined constant pulling force, wherein:
• the winch motor is an electrical winch motor;
• applying power to the winch motor comprises applying electrical current to the electrical winch motor;
• and adjusting the power to the winch motor comprises adjusting the electrical current applied to the electrical winch motor to achieve the predefined constant pulling force;
• when it is determined that the distance from the center axis of rotation to the top layer of winch cable has increased, increasing the electrical current applied to the electrical winch motor so as to maintain the predefined constant pulling force and when it is determined that the distance from the center axis of rotation to the top layer of winch cable has decreased, decreasing the electrical current applied to the electrical winch motor so as to maintain the predefined constant pulling force;
• and
• determining a number of layers of winch cable wound around the winch drum based on the determined distance from the center axis of rotation of the winch drum to the outer edge of the top layer of the winch cable and turning off the electrical winch motor in response to the applied electrical current to the electrical winch motor being greater than a threshold current for the determined number of layers, where each different number of layers has a different threshold current for turning off the electrical winch motor.

A non-transitory computer readable medium storing a computer program, wherein when a control system of a winch system executes the computer program the winch system performs the steps of:

• setting a predefined constant pulling force for the winch system;
• determining a number of windings of a winch cable wound around a rotatable winch drum of the winch system;
• applying power to a winch motor of the winch system, via the control system, to rotate the winch drum and achieve the predefined constant pulling force based on the determined number of windings;
• monitoring the number of windings of the winch cable wound around the winch drum;
• determining whether a change is detected in the number of windings of the winch cable;
• and in response to the number of windings of the winch cable changing, adjusting the power applied to the winch motor, via the control system, to maintain the predefined constant pulling force, wherein:
• the winch motor is an electric winch motor;
• applying power to the winch motor comprises applying electrical current to the electric winch motor;
• and adjusting the power to the winch motor comprises adjusting the electrical current applied to the electric winch motor such that when it is determined that the number of windings of the winch cable wound around the winch drum has increased, the electrical current applied to the electric winch motor is increased so as to maintain the predefined constant pulling force, and when it is determined that the number of windings of the winch cable wound around the winch drum has decreased, the electrical current applied to the electric winch motor is decreased so as to maintain the predefined constant pulling force, and wherein:
• the winch system includes a load limiter and the control system performs the additional steps of:
• in response to the determined number of windings being at a threshold layer number, turning off the electric winch motor in response to the electrical current of the electric winch motor being greater than a threshold current for the threshold layer number, where each layer number has a different threshold current for turning off the electric winch motor.

A constant load winch comprising:

• a rotatable winch drum;
• a winch cable that can be wound about and unwound from an outer surface of the winch drum, relative to an axis of rotation of the winch drum;
• a winch motor that drives rotation of the winch drum;
• a constant load winch control system including a sensor that senses a number of layers of winch cable wound about the winch drum;
• a control system configured to output a control signal to the winch motor to control the winch motor to achieve a constant pulling force on the winch cable based on the number of layers sensed by the sensor and limit a hydraulic pressure to the winch motor when a hydraulic pressure of the winch motor is greater than a threshold hydraulic pressure for the determined number of layers, where for each different number of layers wound around the winch drum, there is a different threshold hydraulic pressure for limiting the hydraulic pressure to the winch motor;
• and a plurality of pressure relief valves adapted to open when the winch reaches an associated threshold hydraulic pressure, where for each different number of layers wound around the winch drum, there is a different associated pressure relief valve adapted to open at a different threshold hydraulic pressure for that layer.