<P> For a given robot the only parameters necessary to completely locate the end effector (gripper, welding torch, etc .) of the robot are the angles of each of the joints or displacements of the linear axes (or combinations of the two for robot formats such as SCARA). However, there are many different ways to define the points . The most common and most convenient way of defining a point is to specify a Cartesian coordinate for it, i.e. the position of the' end effector' in mm in the X, Y and Z directions relative to the robot's origin . In addition, depending on the types of joints a particular robot may have, the orientation of the end effector in yaw, pitch, and roll and the location of the tool point relative to the robot's faceplate must also be specified . For a jointed arm these coordinates must be converted to joint angles by the robot controller and such conversions are known as Cartesian Transformations which may need to be performed iteratively or recursively for a multiple axis robot . The mathematics of the relationship between joint angles and actual spatial coordinates is called kinematics . See robot control </P> <P> Positioning by Cartesian coordinates may be done by entering the coordinates into the system or by using a teach pendant which moves the robot in X-Y-Z directions . It is much easier for a human operator to visualize motions up / down, left / right, etc. than to move each joint one at a time . When the desired position is reached it is then defined in some way particular to the robot software in use, e.g. P1 - P5 below . </P> <P> Most articulated robots perform by storing a series of positions in memory, and moving to them at various times in their programming sequence . For example, a robot which is moving items from one place to another might have a simple' pick and place' program similar to the following: </P> <P> Define points P1--P5: </P>

When were robots first used in car manufacturing