Kinematics and Guardian Dimensions

The following images show the offsets between the origin of the Guardian system and the WAM origin as defined on the WAM Kinematics, Transmission Ratios, and Joint Ranges page. The WAM software package follows the convention defined on that page and the ROS model contains separate nodes for the Guardian and WAM, so it makes sense to fully define the system geometry in this way.

The origin of the Guardian is conventionally defined relative to its patch of contact with the ground. This situates the origin in the geometrical center of the Guardian. The WAM origin (as used by the WAM software) is then defined relative to the Guardian origin.

Because the origin is located equidistant from all points of contact with the ground, its center of rotation when performing in-place rotations is the Z-axis, assuming equal conditions for each wheel/tread (traction, tire pressure, contact area, etc.).

Without Wheels (Treads Only)

Figure 1: Profile of GWAM without wheels. In this configuration, the origin is equidistant from the ends of the 600 mm-long contact patch and 220 mm above the ground.

Figure 2: Top view of GWAM without wheels. In this view, the origin is equidistant from the centers of contact that are 448 mm apart, along the centerline of the robot.

With Wheels and Treads

Figure 3: Front view and profile of GWAM with wheels. With wheels, the origin is 329 mm from the ground instead of 220.

Figure 4: Top view of GWAM with wheels. The contact patches are now 673 mm apart left to right instead of 448. The wheel contact points are 600 mm apart.