Patent GB-1080277-A (GB)
Title: Adaptive control system for numerically controlled machine tool
IPC: G05B19/416
Filed: 1965-08-16
Abstract: 1,080,277. Programmed control of machine tools. BENDIX CORPORATION. Aug. 16, 1965 [Aug. 24, 1964], No. 34973/65. Heading G3N. In a programmed numerical control system 20, such as disclosed in Specifications 848, 647 and 931,048, an adaptive controller 22 is provided to modify the operation of the numerical control system to optimize the machining performance. Information relating to the desired feed and speed of a spindle and geometry of a desired part is read by a tape reader 24 and fed to a numerical control unit 26 which provides motion commands 36 to servodrives 34 together with feed and speed signals 38, 40 corrected by the outputs of the adaptive controller 22. Feedback from the servodrives to the control unit 26 is provided by position transducers 42. The speed signal 38 controls the rate of rotation of a milling machine spindle at a tool work interface 44 and the feed signal controls the feed of the tool with respect to the workpiece. A plurality of sensors 46 measure the tool tip average temperature, vibration of the cutting tool and the torque exerted on the cutting tool. The outputs of the sensors are applied on lines 48, 50, 52 to a data reduction subsystem 54 also having as inputs the corrected feed and speed signals from lines 38, 40, constraints limits on line 56, representing maximum and/or minimum values of spindle speed, feed, torque, vibration and temperature, constants relating to the depth and width of cut on line 58, and constants relating to tool wear on line 60. These signals are interpreted in an analog manner to derive a tool wear rate signal on a line 64 and a metal removal rate signal on a line 66 which are fed to a performance computer 62: the performance computer 62 is also provided with performance criteria signals on line 73 and cost constants signals on line 74, set up on potentiometers, and processes the supplied signals to derive a pulse train representative of a figure of merit for cutting operation which is fed to an optimization computer 68. Signals on lines 70, 72 representative of violation of the constraint limits and indicative of cutting being in progress are also fed to the optimization computer 68 from the subsystem 54. The optimization computer operates on a digital basis to provide feed or speed correction signals to the numerical control unit 26. It first makes an exploratory incremental change in either feed or speed, determines after a settling down period the change caused in the figure of merit. It then makes an experimental change in the other quantity, and again determines the change in the figure of merit. The feed and speed are then simultaneously changed in directions determined by the sense of the change in the figure of merit and by amounts proportional to the changes in the figure of merit. This sequence is repeated to optimize the operation of the system and to follow changes in the optimum which occur as a result of variation in the metal cutting conditions. The presence of a constraint violation initiates a special sub-routine designed to correct the violation.