From the beginning robot arm kinematics followed four basic geometrics:
and these configurations still dominate the products offered by the major suppliers. But in 1988 any discussion must acknowledge the SCARA concept (Figure 2.1), the brainchild of Professor Makino of Yamanashi University. SCARA, which stands for Selective Compliance Assembly Robot Arm, does not contribute so much in terms of sheer kinematics - it delivers wrist and end effectors in pretty much the same way as cylindrical coordinates, albeit with a smaller vertical excursion - rather, in focusing on assembly operations, Makino saw benefits in having a robot arm compliant in horizontal motions while being quite rigid in vertical motions. A SCARA arm can extract parts from a pallet and move them to a work station for “pancake” assembly. This requires little vertical motion; and, when a part comes into contact with the workpiece, horizontal compliance is forgiving if alignment is not precise.
Unable to display preview. Download preview PDF.