Robot guidance using multiple frames

1 . A computer-implemented method of tracking a position of a tool relative to a workpiece mounted on a workpiece holder, the method comprising:

i) identifying a first frame of reference defining the position of the workpiece;

ii) identifying a second frame of reference defining a position of a machining head of the tool attached to a robotic arm, the tool being moveable relative to the workpiece using the robotic arm and further comprising a clamp moveable relative to the machining head;

iii) identifying a third frame of reference defining a position of the clamp;

iv) actuating the robotic arm to move the tool to a first target position relative to the workpiece;

v) operating the clamp to apply a clamping force on the workpiece;

vi) measuring a position of the third frame of reference; and

vii) updating an offset to the first target position based on movement of the third frame of reference after operating the clamp.

2 . A computer-implemented method of tracking a position of a workpiece relative to a tool, the method comprising:

i) identifying a first frame of reference defining the position of the workpiece, the workpiece being attached to an end of a robotic arm;

ii) identifying a second frame of reference defining a position of a machining head of the tool, the tool further comprising a clamp moveable relative to the machining head;

iii) identifying a third frame of reference defining a position of the clamp;

iv) actuating the robotic arm to move the workpiece to a first target position relative to the tool;

v) operating the clamp to apply a clamping force on the workpiece;

vi) measuring a position of the first frame of reference; and

vii) updating an offset to the first target position based on movement of the first frame of reference after operating the clamp.

3 . The method of claim 1 , wherein the first frame of reference is identified based on a plurality of datums on the workpiece holder and/or on the workpiece.

4 . The method of claim 1 , wherein the second frame of reference is identified based on a plurality of datums on the machining head.

5 . The method of claim 1 , wherein the third frame of reference is identified based on a plurality of datums on the clamp.

6 . The method of claim 1 , wherein the first, second and third frames of reference each define a three dimensional position and orientation of a point on the workpiece, machining head and clamp respectively.

7 . The method of claim 1 , wherein the method is repeated for a plurality of target positions on the workpiece.

8 . The method of claim 7 , wherein an offset is stored for each of the plurality of target positions.

9 . The method of claim 1 , wherein iv) to vii) are repeated in response to the measured position of the third or first frame of reference being outside of a predetermined tolerance.

10 . The method of claim 1 further comprising operating the machining head to machine the workpiece.

11 . The method of claim 10 , wherein a clamping force applied by the clamp during machining the workpiece is updated based on a measure of movement of the third frame of reference relative to the first frame of reference during machining of the workpiece.

12 . The method of claim 11 , wherein the clamping force is increased if the measure of movement exceeds a predetermined range.

13 . A non-transitory computer readable medium comprising a computer program stored thereon comprising instructions for causing a computer system to perform the method according to claim 1 when the instructions are executed by the computer system.

14 . A robotic drilling system comprising:

a robotic arm having a tool attached thereto, the tool comprising a machining head and a clamp moveable relative to the machining head;

a workpiece holder configured for mounting a workpiece to be machined;

a metrology system configured to measure a position of the workpiece and positions of the machining head and clamp relative to the workpiece;

a controller connected for control of the metrology system, robotic arm and tool,

wherein the controller is configured to:

i) identify, using the metrology system, a first frame of reference defining a position of the workpiece;

ii) identify, using the metrology system, a second frame of reference defining a position of the machining head;

iii) identify, using the metrology system, a third frame of reference defining a position of the clamp;

iv) actuate the robotic arm to move the machining head to a first target position relative to the workpiece;

v) operate the clamp to apply a clamping force on the workpiece;

vi) measure, using the metrology system, a position of the third frame of reference; and

vii) update an offset to the first target position based on movement of the third frame of reference after operating the clamp.

15 . A robotic system comprising:

a robotic arm having a workpiece attached thereto;

a tool comprising a machining head and a clamp moveable relative to the machining head;

a metrology system configured to measure a position of the workpiece and positions of the machining head and clamp;

a controller connected for control of the metrology system, robotic arm and tool,

wherein the controller is configured to:

i) identify, using the metrology system, a first frame of reference defining a position of the workpiece;

ii) identify, using the metrology system, a second frame of reference defining a position of the machining head;

iii) identify, using the metrology system, a third frame of reference defining a position of the clamp;

iv) actuate the robotic arm to move the workpiece to a first target position relative to the tool;

v) operate the clamp to apply a clamping force on the workpiece;

vi) measure, using the metrology system, a position of the first frame of reference; and

vii) update an offset to the first target position based on movement of the first frame of reference after operating the clamp.

16 . The system of claim 14 , wherein the first frame of reference is defined by a plurality of datums on the workpiece holder and/or on the workpiece.

17 . The system of claim 14 , wherein the second frame of reference is defined by a plurality of datums on the machining head.

18 . The system of claim 14 , wherein the third frame of reference is defined by a plurality of datums on the clamp.

19 . The system of claim 14 , wherein the first, second and third frames of reference each define a three dimensional position and orientation of a point on the workpiece, machining head and clamp respectively.

20 . The system of claim 14 , wherein the controller is configured to repeat steps i) to vii) for a plurality of target positions on the workpiece.

21 . The system of claim 14 , wherein the controller is configured to store an offset for each of the plurality of target positions.

22 . The system of claim 14 , wherein the controller is configured to repeat iv) to vii) if the measured position of the third or first frame of reference is outside of a predetermined tolerance.

23 . The system of claim 14 , wherein the controller is configured to operate the machining head to machine the workpiece.

24 . The system of claim 23 , wherein the controller is configured to apply a clamping force by the clamp during machining the workpiece and update the offset based on a measure of movement of the third frame of reference relative to the first frame of reference during machining of the workpiece.

25 . The system of claim 24 , wherein the controller is configured to increase the clamping force if the measure of movement exceeds a predetermined range.