Optical automatic seam tracker and real time control system for an industrial robot

A method of operating a robot system including:

• a robot controller for iteratively controlling an effector end with an error compensating control signal in relation to a taught path;
• a seam sensor system having a sensor disposed ahead of the effector end for iteratively deriving data representing discrete successive sensed locations upon the seam ahead of the effector end, the robot controller iteratively providing a first signal representative of the present effector end position;
• and a control processor responsive to said first signal and to said sensed locations representative data for generating said control signal as an indication of an error between effector end position and sensed seam location;
• comprising the following operative steps by the control processor:
• calculating and storing iteratively, in response to said control signal and to said first signal, the elapsed distance of the effector end from the first down to the present effector end position;
• calculating and storing iteratively, in response to said control signal and to said first signal, the elapsed distance from the first down to the present sensed seam location by correlation with the distance between the effector end and the sensor;
• ordering and storing said data by reference to, and correlating said successive sensed locations with, said sensed location elapsed distances to provide a look-up table thereof;
• deriving iteratively with said first signal for a present effector end position and with said control signal for a present positioning of the effector end successive positions representing the taught path as recovered therefrom;
• extrapolating by a predetermined amount from past positions on said recovered taught path to an anticipated position thereon;
• extrapolating by said predetermined amount from past elapsed distances to an anticipated elapsed distance for said effector end;
• determining from said anticipated elapsed distance in relation to said stored sensed location elapsed distances of said look-up table a corresponding anticipated sensed location;
• comparing said anticipated sensed location with said anticipated recovered taught path position for deriving a present control signal in relation to said anticipated effector end position;
• and
• controlling by feedforward the robot controller in response to said present control signal;
• thereby to move the effector end to said anticipated position following each past position of the effector end and each past control signal therefor.

In a robot system including a robot controller for controlling an effector end along a seam in relation to a taught path and a seam tracker control system, the seam tracker control system, including a sensor, for sensing the seam ahead of the effector end and for deriving data representing discrete successive sensed locations upon the seam, and a control processor responsive to said seam tracker control system and to said robot controller for deriving a control signal representative of an error between effector end positioning and a matching sensed location, the effector end being controlled by said robot controller in response to said control signal to provide seam tracking with the effector end;

• the combination of:
• means responsive to said robot controller and associated with said control processor for successively calculating the distances between two consecutive sensed locations, for accumulating said distances to provide iteratively the elapsed distance down to the last sensed location and for providing orderly samples each classified by elapsed distance to identify the respective sensed locations upon the seam;
• look-up table means for storing data representing coordinates derived by the sensor system for each of said sensed locations in relation to and in the order of said orderly samples;
• with the control processor being successively responsive to a present and a last position of said effector end for extrapolating therefrom to an anticipated position and for deriving an anticipated elapsed distance thereto;
• with the control processor being operative with said look-up table for correlating said anticipated elapsed distance of the effector end with closely related samples of said look-up table to derive coordinates for an anticipated location on the seam corresponding to such anticipated elapsed distance;
• with the control processor deriving a present control signal in relation to said derived coordinates;
• and
• the control processor controlling the robot controller with said control signal so as to effectuate feedforward control of the effector end toward a new position defined by said anticipated location.

A method of operating a robot system including:

• a robot controller for iteratively controlling an effector end with an error compensating control signal in relation to a taught path;
• said robot controller providing a first signal representative of the present effector end position;
• a seam sensor system having a sensor disposed ahead of the effector end for iteratively deriving data representing discrete successive sensed locations upon the seam ahead of the effector end;
• a control processor for generating and applying to said robot controller said control signal as an indication of an error between effector end and sensed seam location;
• comprising the following operative steps by the control process:
• applying to said control processor said first signal;
• applying to said control processor a reference signal characteristic of the spatial relation between a present effector end position and a present seam location;
• calculating and storing iteratively, in response to said control signal and to said first signal, the elapsed distance of the effector end from the first down to the present effector end position;
• calculating and storing iteratively, in response to said control signal and to said first signal, the elapsed distance from the first down to the present sensed seam location by correlation with the distance between the effector end and the sensor;
• ordering said data by reference, and correlating said successive sensed locations with, said sensed locations elapsed distances to provide a look-up table thereof;
• deriving iteratively with said first signal for a present effector end position and with said control signal for a present positioning of the effector end successive positions representing the taught path as recovered therefrom;
• extrapolating by a predetermined amount from past positions on said recovered taught path to an anticipated position thereon;
• extrapolating by said predetermined amount from past elapsed distances to an anticipated elapsed distance for said effector end;
• interpolating said anticipated elapsed distance with at least two bounding said sensed locations elapsed distances in said look-up table for deriving a corresponding anticipated sensed location;
• correcting said anticipated sensed location in relation to said reference signal to provide an anticipated effector end position;
• comparing said anticipated effector end position with said anticipated recovered taught path position for deriving a present control signal in relation to said anticipated effector end position and said reference signal;
• and
• controlling by feedforward the robot controller in response to said present control signal;
• thereby to move the effector end to said anticipated position following each past position of the effector end and each past control signal therefor.

In a robot system including a robot controller for controlling an effector end along a seam in relation to a taught path and a seam tracker control system, the seam tracker system including a sensor system for sensing the seam ahead of the effector end and for deriving data representing discrete successive sensed locations upon the seam, and a control processor responsive to said sensor system and to said robot controller for deriving a control signal representative of an error between an effector end present position and a new position matching a sensed location, the effector end being controlled by said robot controller in relation to a present effector end position representative signal derived from said robot controller and to said control signal to provide continuous operation upon the seam with said effector end;

• the combination of:
• means responsive to said robot controller and associated with said control processor for successively calculating the distances between two consecutive sensed locations, for accumulating said distances to provide iteratively the elapsed distance down to the last sensed location and for providing orderly samples each representing such elapsed distance to identify the respective sensed locations upon the seam;
• look-up table means for storing data representing coordinates derived by the sensor system for each of said sensed locations in relation to and in order of said orderly samples;
• means within said control processor successively responsive to a present and a last position of said effector end for extrapolating therefrom to an anticipated position and for deriving an anticipated elapsed distance thereto;
• means responsive to a reference signal and operating within said control processor with said look-up table for correlating said anticipated elapsed distance of the effector end with a corresponding sample of said storing means to derive corresponding coordinates of an anticipated effector end location on the seam;
• comparator means within said control processor for deriving a present control signal in relation to said corresponding coordinates;
• and
• the control processor controlling the robot controller with said present control signal so as to effectuate feedforward control of the effector end toward a new position defined by said anticipated elapsed distance.