Visual Servoing Methodology
Visual Servoing techniques are broadly classified into the following types
- Image Based (IBVS)
- Position Based (PBVS)
- Hybrid Approach
IBVS was proposed by Weiss and Sanderson. The control law is based on the error between current and desired features on the image plane, and does not involve any estimate of the pose of the target. The features may be the coordinates of visual features, lines or moments of regions. IBVS has difficulties with motions very large rotations, which has come to be called camera retreat.
PBVS is sometimes referred to as Pose-Based VS and is a model-based technique (with a single camera). This is because the pose of the object of interest is estimated with respect to the camera and then a command is issued to the robot controller, which in turn controls the robot. In this case the image features are extracted as well, but are additionally used to estimated 3D information (pose of the object in Cartesian space), hence it is servoing in 3D.
Hybrid approaches use some combination of the 2D and 3D servoing. There have been a few different approaches to hybrid servoing
- 2-1/2-D Servoing
- Motion Partition Based
- Partitioned DOF Based
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