External Trajectory Control is a special (non-standard) mode of operation that enables a host computer to generate a robot's trajectory. The host is responsible for sending a continuous stream of absolute or incremental joint position setpoints to a Guidance Controller at a 1kHz rate using standard Ethernet UDP packets. All commands are in joint coordinates, therefore, the host is responsible for implementing any kinematic conversations required for performing any desired Cartesian motions. Applications where the External Trajectory Control technique is of use include telerobotics, haptics and compliant mechanism control.
This mode utilizes a proprietary protocol that defines the contents of the command messages from the host computer as well as status messages that are sent back from the robot. The command messages are continuously streamed from the host and permit it to: define the motion of each axis of a robot; enable motor power; home the robot; dynamically adjust servo PID parameters on the fly; and set digital output values. The continuous stream of returned status messages include the current position of each axis as well as the value of various digital input signals.
This mode of operation includes special means for dealing with lost command packets, which always occur during normal communications, in order to provide smooth operation of the robot.
When the controller is operating in this mode, all robot motions are controlled by the host computer. Normal GPL programs cannot control the robot in any way.
Since this mode of control places very high demands on the host computer and the controller and requires a detailed knowledge of trajectory generation, Ethernet communications, operating systems and the proprietary communication protocol, this mode is only offered as a special feature. If you have a special application that requires this sophisticated level of control, please contact Brooks to discuss special engineering fees for training and support.