Patent GB-1423547-A (GB)
Title: Control arrangement for position control of a member
IPC: G05B19/35
Filed: 1973-05-31
Abstract: 1423547 Automatic control of positioning VEREINIGTE FLUGTECHNISCHE WERKEFOKKER GmbH 31 May 1973 [31 May 1972] 25971/73 Heading G3N In a program controlled positioning system, a position control loop for each degree of positional freedom contains a secondary speed control loop under the control of a computer 41 receiving additional information (maximum acceleration and speed, system load) controlling the speed of a member to be positioned. As shown a digital central control unit 20, see also Fig. 2 (not shown) for a manipulating, lacquer spraying, or welding system receives manual (21) or program (22) information as well as information from interface (28) enabling conjoint operation with other remote manipulating, welding, or lacquering systems and controls control loops (30-32) for positioning gripping device (14), Fig. 1 (not shown) in vertical and horizontal translational, and rotation about a vertical axis, degrees of freedom respectively. Units (33-35), Fig. 2 represent control of opening and closing, rotating, and pivoting of gripping device (14). For each loop (30-32) control unit 20 provides a commanded final position signal SE for the program step, which is compared with actual position signal Si the error being fed to analogue computer 41, which can be a model of the system in a control loop. Computer 41 also receives additional information from unit 20, and provides a speed function signal V s  (t), calculated to minimize the travel time without overswing. Signal V s  (t) is compared with an actual speed signal V i  (t) from tacho-alternator 47, the resultant, via controller 43, amplifier 44 and low inertia, ironless disc rotor motor 45 controlling the corresponding positional degree of freedom via transmission 46. Motor current is monitored to provide the system load additional information to computer 41. Programming arrangement. The program is constituted by a pre-set cross bar distribution panel, Fig. 4 (not shown), each of whose columns represents a step in the program, the rows representing: (i) a four-bit binary number for each positional degree of freedom, each number representing an address to a position register (27), Fig. 2 in the form of a multi-ganged potentiometer with setting indicators in the form of lights, and providing the commanded position signals to the loops: (ii) program delay in dependence on gripper operation: (iii) call up one of sub-routines (24-26), Fig. 2 used for repeating identical program portions, the main program not stepping until the sub-routine is complete: there being a row for each sub-routine. Program stepping rate may vary from step-to-step, each step requiring completion of the previous one, and no error indicating outputs from the system, to implement the next step. A pre-programmed non-optional speed may be programmed for each step, and comes into play if a program signal in a variable speed row of the program panel is provided. Gripper control may be independent of the program, and hydraulically or pneumatically operated. The program may be stopped at any step, or returned to the start. The manipulating system transfers workpieces between processing stations.