The graphical simulation has been used to develop different control algorithms for the robotic manipulators. Below are some time lapsed screenshots showing Ranger moving under some of these control schemes.
To help facilitate coordinated motion between multiple arms an control mode was developed allowing one arm to track the motions of another.
|This figure shows the video arm (the arm at the top of the image) tracking the position of the right dexterous arm. The operator directly controls the right arm, and the video arm will maintain the same relative position automatically. The resultant video from that arm would give the effect of a camera attached to the arm at a fixed location in space.|
|Although translational motion is automatically tracked, the operator can still control the angle of the tracking arm. This picture shows the video manipulator performing a local pitch while tracking to the right dexterous arm. The center of rotation in this case is at the tool tip of the right arm. This allows the operator to control the video camera's viewpoint and orbit partially around the tool on the right arm.|
The grapple arm is typically controlled similar to any other arm. The operator controls the arm forward to grab a fixture on the worksite. Once the grapple arm has attached itself to the worksite, most operators want the kinematics to be reversed so that a forward motion will no longer extend the grapple arm. Instead, a forward command should move the body of ranger closer toward the workspace. A new control mode is used to do this, in pilot mode the attached manipulator will seem to move the vehicle as its end effector.
||This picture shows a yaw rotation of the grapple arm in pilot mode. Note that the point of rotation is not at the end effector of the grapple arm. Instead the center of rotation is the manipulator module on the vehicle itself.|
|This picture shows a side translation in pilot mode. The resultant motion in the grapple arm is to cause the vehicle body to sidestep to its right and left. This mode makes it easier for the operator to reposition the vehicle when they are attached to the worksite.|
The use of active attitude compensation allows the operator to easily move an arm to grab an object while the vehicle is free floating. Without this compensation, the arm and vehicle dynamics are coupled causing the vehicle to displace whenever the arm moves.
||This screenshot shows a large arm deflection with the active attitude compensation turned on. Even a large change in the arm the body incurs only a small perturbation. The active compensation allows for operators to move the manipulators independently without concern of the overall dynamics which could cause the body to move.|
|Without this compensation, even a small deflection of the arm causes the coupled dynamics to rotate the vehicle body. The vehicle itself now compensates for all of the manipulator's motions. This can make it difficult for an operator to grab an object while free floating, since extending the arm will cause the body to move back thus limiting the relative extension the manipulator can achieve. Also since the arm dynamics are coupled to the body, any movement of the arm will cause motion in the body that the operator would have to compensate for.|