Medical robotic system with sliding mode control

A medical robotic system having a master input device, a plurality of joints coupled to corresponding of a medical device or a robotic arm for moving the medical device, and a processor responsive to user manipulation of the master input device to control movement of one of the plurality of joints, wherein the improvement comprises configuration of the processor to control such movement by:

• computing a distance from a sliding surface using at least a position error associated with commanded movement of the joint;
• computing a reaching law gain as a function of the absolute value of the distance;
• computing a current state for an integrator using a prior state of the integrator and the distance;
• computing a product of the reaching law gain and the distance;
• limiting the product to be less than a maximum control action;
• modifying the current state of the integrator using the limited product value so as to limit a sum of the product and the current state of the integrator to be less than the maximum control action;
• computing a sliding mode control action by summing the product and the modified current state of the integrator;
• and
• processing the sliding mode control action to generate one or more command signals to drive the joint according to the user manipulation of the master input device.

A method for controlling a joint coupled to a medical device or a robotic arm adapted to move the medical device, in response to user manipulation of a master input device, comprising;

• computing a distance from a sliding surface using at least a position error associated with commanded movement of the joint;
• computing a reaching law gain as a function of the absolute value of the distance;
• computing a sliding mode control action by multiplying the reaching law gain and the distance;
• limiting the sliding mode control action to be less than a maximum control action;
• and
• processing the limited sliding mode control action to generate one or more command signals to drive the joint according to the user manipulation of the master input device.

A medical robotic system having a master input device, a joint coupled to a medical device or a robotic arm adapted to move the medical device, and a processor responsive to user manipulation of the master input device to control movement of the joint, wherein the improvement comprises the processor being configured to control such movement by:

• computing a distance from a sliding surface using at least a position error associated with commanded movement of the joint;
• computing a reaching law gain using the distance;
• computing a sliding mode control action by multiplying the reaching law gain and the distance;
• limiting the sliding mode control action to be less than a maximum control action,
• processing the limited sliding mode control action to generate one or more command signals to drive the joint according to the user manipulation of the master input device.

A medical robotic system comprising:

• a joint coupled to a medical device or a robotic arm adapted to move the medical device;
• and
• a controller configured to control movement of the joint by:
• computing a distance from a sliding surface using the following equation:
• σ=λ·(QC−QL)+(VC−VL)2,
• wherein σ represents the distance, λ is a parameter value, (QC−QL) is a position error and (VC−VL) is a velocity error associated with commanded movement of the joint;
• computing a sliding mode control action based at least in part on the distance to the sliding surface;
• and causing the joint to be moved at least partially in response to the sliding mode control action.

A medical robotic system comprising:

• a joint coupled to a medical device or a robotic arm adapted to move the medical device;
• and
• a controller configured to control movement of the joint by:
• computing a distance from a sliding surface;
• computing a reaching law gain using the following equation:
• GAIN
• RL
• =
• (
• 
• σ
• 
• RS
• )
• v
• where GAINRL represents the reaching law gain, σ is the distance to the sliding surface, RS is a parameter value, and v is an exponential value between 0 and 1;
• computing a sliding mode control action based at least in part on the distance to the sliding surface and the reaching law gain;
• and causing the joint to be moved at least partially in accordance with the sliding mode control action.