Asea Brown Boveri Ab

John-Erik Snell

Torgny Brog&aring;rdh

Staffan Elfving

A method for control of the movement of the movement of an industrial robot along a given track (P,-P,) with a desired track speed (v), which industrial robot has a number of movement axes and for each axis servo equipment for control of the axis movement in accordance with reference values ({overscore (&tgr;)},) supplied thereto. First, those axis angles ({overscore (&phgr;)},) which are needed for assuming the next position on the track are calculated. In dependence on the calculated axis angles and a first mathematical model, which describes the static and dynamic properties of the robot, for each one of the movement axes that torque ({overscore (&tgr;)}&equals;(&tgr;,, &tgr;,. . . &tgr;,)) is calculated which is required for assuming the next position. The load (t) is calculated at one or more mechanically critical points for the calculated axis angles ({overscore (&phgr;)},) with the aid of a second mathematical model, which describes the load of the robot at the critical points. For each one of the axes, the calculated torque ({overscore (&tgr;)}) is compared with a maximum permissible torque, ({overscore (&tgr;)},), and the load (t) is compared with a maximum permissible load (t,) for the critical point. If the calculated torque exceeds the maximum permissible torque for any axis, or if the calculated load exceeds the maximum permissible load for any critical point, then the track speed (v) is reduced and the reference values for the servo system {overscore (&tgr;)},&equals;(&tgr;,, &tgr;,. . . &tgr;,, are calculated in dependence on the reduced track speed.

Method for control of an industrial robot along a given track

An equipment for calibration of an industrial robot which has a plurality of axes of rotation and wherein, the equipment comprises a measuring device is adapted for rotatable connection to a reference point the position of which is known, is adapted to be in contact with the robot, or a tool carried by the robot, during the calibration process, and has an axis of rotation which intersects the reference point when the measuring device is connected to the reference point. The measuring device further comprises a gravity sensor which is so mounted so that the axis of the gravity sensor is substantially parallel to the axis of rotation of the measuring device, whereby the gravity sensor measures the angle between the gravity vector and axis of rotation.

Device and method for calibration of a multi-axis industrial robot

Method and device for calibration of movement axes of an industrial robot

In a calibration method for an industrial robot (2-6), a calibration tool (8) supported by the robot hand (6) is brought into contact a spherical calibration body (7) with a known radius. Thereafter, the output signals from the position transducers of the robot axes are read and stored. This method is repeated a plurality of times with different robot configurations. Thereafter, the calibration parameters of the robot are calculated starting from the kinematic equations of the robot, a model of the relationship between axial position and position transducer signal, the known radius of the calibration body, and the read and stored position transducer signals.

A method for controlling an industrial robot such that a tool supported by the robot is able to follow a path which is determined by a number of consecutive points, and wherein the robot while following the path ends up near or a singularity. The robot has a plurality of movement axes and its configuration is determined by the angles of rotation of the movement axes. The angles of rotation which are to be assumed by the robot in order to obtain the desired position and orientation for the tool at the next point on the path are calculated by an iterative method. The ratio of the angular velocities of the axes to the velocity of the tool is given by a Jacobian matrix. By means of the Jacobian matrix it is determined whether the robot is at or near a singularity. The intention of the invention is to control the iteration such that the position of the tool remains correct through the singularity. A certain error in the orientation of the tool may be accepted. At a singularity the importance of the position errors is increased by weighting these errors during the iteration in relation to the orientation errors while at the same time locking the singular axes.

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Vaster.ang.s, Sweden

John-Erik Snell