Coordinate positioning system

The method of operating a machine having two coordinate drives cooperating to produce a resultant movement of a driven member, comprising:

• (a) determining first and second velocities for movement of the driven member along respective paths having a point of intersection;
• (b) determining in respect of each velocity a pair of component velocities;
• (c) determining a first velocity profile between one component of the first velocity and the corresponding component of the second velocity and determining a corresponding second velocity profile being a scaled version of the first velocity profile;
• (d) a resultant velocity profile of the first and second velocity profiles defining a curve joining said paths, and having a start point and an end point;
• (e) the resultant velocity profile having at said start point a first pair of component velocities the same as those of the first velocity;
• (f) the resultant velocity profile having at said end point a second pair of component velocities the same as those of the second velocity;
• (g) defining a start point and an end point on the respective paths at which the curve is joinable thereto;
• and
• (h) actuating said coordinate drives sequentially in accordance with the component velocities of the first velocity, with the first and second velocity profiles of the curve, and with the component velocities of the second velocity.

A method of operating a coordinate positioning machine to accelerate a head of the machine, the method comprising the steps of:

• determining, on the basis of first and second velocities and a predetermined acceleration function, a time interval required to accelerate the head from the first to the second velocity;
• determining on the basis of the time interval a curved velocity profile for accelerating the head from the first to the second velocity;
• and
• driving the head according to the curved velocity profile.

A method of operating position drives of a coordinate positioning machine, to accelerate a head of the machine through a change in velocity from a first velocity to a second velocity, comprising the steps of:

• determining on the basis of the first and second velocities, and of a constant absolute value for rate of change of acceleration, a time interval required to accelerate the head from the first to the second velocity;
• determining on the basis of the time interval a velocity profile for accelerating the head from the first to the second velocity;
• generating a drive signal representing the velocity profile;
• and
• applying the drive signal to the positioning drives of the coordinate positioning machine, thereby to accelerate the head from the first to the second velocity.

Apparatus for operating positioning drives of a coordinate positioning machine, to accelerate a head of the machine through a change in velocity from a first velocity to a second velocity, comprising:

• means for determining on the basis of the first and second velocities, and of a constant absolute value for rate of change of acceleration, a time interval required to accelerate the head from the first to the second velocity;
• means for determining on the basis of the time interval a velocity profile for accelerating the head from the first to the second velocity;
• means for generating a drive signal representing the velocity profile;
• and
• means for applying the drive signal to the positioning drives of the coordinate positioning machine, thereby to accelerate the head from the first to the second velocity.