Medical instrument with programmable torque control

A medical instrument including:

• a tool;
• a brushless motor coupled to said tool for driving said tool through a repetitive path of movement at a selected speed, said motor being actuated to operate at said selected speed in response to an application of multi-phase pulse width modulated signals thereto, said motor developing a torque in response to movement of said tool;
• a driver connected to said motor, said driver including a plurality of transistors that are selectively switched between a voltage source and ground to generate a plurality of pulse width modulated signals for application to said motor, said transistors being switched in response to the application of driver control signals thereto and said transistors having a current flowing therethrough representative of said torque developed by said motor;
• a speed sensor connected to said motor for monitoring said speed of said motor and producing a speed signal representative of said speed of said motor;
• a current sensor connected to said driver transistors for producing a transistor current signal representative of said current flowing through said transistors;
• a speed regulator connected to said speed sensor for receiving said speed signal, said speed regulator being configured to compare said speed signal to a speed setpoint speed signal representative of a selected motor speed and to produce a speed error signal based on said comparison;
• a torque regulator connected to said speed regulator for receiving said speed error signal, said torque regulator being configured to compare said speed error signal to a torque limit signal representative of a selected maximum torque and to produce a selectively adjusted speed error signal based on said comparison;
• and
• a driver controller connected to said current sensor for receiving said transistor current signal and to said torque controller for receiving said adjusted speed error signal and to said driver, said driver controller being configured to compare said transistor current signal with said adjusted speed error and to produce said driver control signals in response to said comparison, wherein said driver control signals are of a sufficient potential so that said transistors alternatively connect said motor between the voltage source and ground.

A medical instrument including:

• a tool;
• a motor coupled to said tool for driving said tool through a repetitive path of movement at a selected speed, said motor being actuated to operate at said selected speed in response to an application of a variable motor energization signal thereto;
• a speed monitor connected to said motor for producing a motor speed signal representative of said speed of said motor;
• a motor controller connected to said motor for applying said motor energization signal thereto and to said speed monitor for receiving said motor speed signal therefrom, said motor controller being configured to compare said speed signal to a speed setpoint signal and, in response to said comparison, to vary said motor energization signal to cause said motor to operate at a selected speed;
• and
• an instrument control assembly including:
• a maximum speed input device for generating a maximum speed signal in response to the inputting of a user-selected maximum tool speed;
• a speed control input device for generating a user speed signal in response to the inputting of a user-selected real time speed command;
• and
• an instrument controller connected to said speed monitor to receive said motor speed signal, to said maximum speed input device for receiving said maximum speed signal, to said speed control input device for receiving said user speed signal and to said motor controller, said instrument controller being configured to generate said speed setpoint signal for application to said motor controller as a function of said user speed signal and a variable function ratio and to compare said user speed signal to said maximum speed signal wherein, when said comparison of said user speed signal to said maximum speed signal indicates said motor is to be operated at the maximum speed, said instrument controller is further configured to compare said motor speed signal to said maximum speed signal and, based on said comparison, to adjust said function ratio.

A method of regulating the speed of motor of a medical instrument, the medical instrument having a tool attached to the motor, the motor being designed to operate at selected speeds in response the application of a modulated power signal thereto, said method including the steps of:

• generating a motor speed signal representative of the speed of the motor;
• generating a maximum speed signal representative of a maximum speed at which the motor is to operate;
• generating a user speed signal representative of a speed which the user wants the motor to operate at;
• comparing said user speed signal to said maximum speed signal;
• when said user speed signal-maximum speed signal comparison indicates said motor is to operate below said maximum speed, generating a speed setpoint signal as a function of a said user speed signal and a function ratio;
• applying said motor speed signal and said speed setpoint signal to a motor controller, said motor controller comparing said motor speed signal and said speed setpoint signal and, based on said comparison, generating a modulated power signal for application to the motor;
• when said user speed-maximum speed comparison indicates the motor is to be operated at the user-selected maximum speed, generating a speed setpoint signal based on said function ratio that is representative of said maximum speed, applying said maximum speed setpoint signal to said motor controller and comparing said motor speed signal to said maximum speed and based on said motor speed signal-maximum speed signal comparison, adjusting said function ratio to cause the generation of a speed setpoint signal that causes said motor to operate at said maximum speed.