Abstract: In reference point return control, a grid point position at which a one-revolution signal (RTS) is first generated by a rotary encoder (24) following restoration of a deceleration limit switch (29) is adopted as a reference point. When a zero point return mode (ZRN="1") for returning a movable element to the reference point is in effect, a numerical controller (21) regards the position at which the one-revolution signal (RTS) is generated by the rotary encoder (24) as being zero. A commanded position REF.sub.n, until the next one-revolution signal is generated, is monitored at every predetermined time, such monitoring of the commanded position being repeated until the movable element arrives in the vicinity of the reference point. When the movable element approaches the reference point and the deceleration limit switch (29) is restored, the commanded position REF.sub.n at an initial time every .sub..DELTA. T is obtained, a distance (N-REF.sub.

Abstract: A tool or a workpiece is fed by the cut feed by cut feed commands during periods when the tool or the workpiece would normally be fed by rapid feed. These periods are chosen to occur when the distance of the sections to be fed is a predetermined distance or less. Then, in the case that the feeding distance is the predetermined distance or less, the tool or the workpiece can be fed more rapidly by cut feed rather than rapid feed. Thus, machining time is shortened to that extent.

Abstract: A digital robot control is provided with digital position, velocity and torque control looping to operate joint motors associated with multiple axes of the robot. Motion programming includes planning and trajectory programs for generating position commands for the control looping on the basis of acceleration, slew and deceleration values that specify robot program specifications for timed moves.

Abstract: An improvement in combination with apparatus including rotary means, wherein the rotary means includes a periphery having indicia printing means and is adapted for feeding a sheet in a path of travel. The improvement comprises: a first device for sensing a time interval during which a sheet having a leading edge is linearly displaced a predetermined distance in the path of travel; a d.c. motor coupled to the rotary mean for rotation of the rotary means; a second device for sensing angular displacement of the rotary means and a computer coupled to the first and second sensing devices and to the d.c.

Abstract: A numerical control apparatus having a feedrate difference reduction capability suitable for use with a multi-axis machine tool. Feedrate differences for respective control axes are calculated from a machining program, and decelerations for the respective control axes are calculated from preestablished allowable feedrate difference settings and the calculated feedrate differences. The control axes are controlled to be displaced within the allowable feedrate difference settings based on the calculated decelerations.

Abstract: A uniform velocity control method for rotating a first movable element (3) at a uniform velocity in a rectilinear-to-rotational motion converting mechanism, in which a second movable element (2c) is moved along a linear shaft (2a) and the first movable element is rotated in dependence upon rectilinear movement of the second movable element. The uniform velocity control method includes (1) a second step of monitoring a position of the second movable element along the linear shaft; (2) a second step of calculating a traveling velocity of the second movable element, which traveling velocity is for rotating the first movable element at a uniform velocity, in dependence upon the position of the second movable element along the linear shaft; and (3) a third step of moving the second movable element at the calculated traveling velocity to make the rotational velocity of the first movable element uniform.

Abstract: The present invention provides an area cutting method for machining an area (AR) bounded by the curve (OLC) of a predetermined external shape previously using a unidirectional cutting motion. The invention has a step of performing cutting along an i-th cutting path (PT.sub.i), a step, executed after completion of cutting along the cutting path (PT.sub.i), of moving a tool (TL) in a cutting-feed mode along the curve (OLC) of the external shape from a machining end point (Q.sub.i) on the cutting path to a machining end point (Q.sub.i-1) on an (i-1)th cutting path (PT.sub.i-1) previously cut, a step of positioning the tool (TL) from the point (Q.sub.i-1) to a machining starting point (P.sub.i) on the cutting path (PT.sub.i), a step of moving the tool in the cutting-feed mode along the curve of the external shape from the machining starting point (P.sub.i) on the cutting path (PT.sub.i) to a machining starting point (P.sub.i+1) on the next cutting path (PT.sub.

Abstract: A method for realizing energy saving, for each of a plurality of mills provided in the hot rolling line, during the pause period until a successive work piece arrives a mill from a preceding work piece separates from a mill. The pause period is forecasted on the basis of a supply interval of work pieces supplied to the rolling line and a period of stay of work piece at each mill, and the mill is set in the pause state within the period defined by subtracting the preparation period required by the mill to reach the steady state from start of operation from such foreseen pause period.

Abstract: To control the intermittent movement of a conveyor belt or carousel, fitted with molds, in a unit for the manufacture of moldings from multi-component plastics, an intended/actual value comparison of the speed of the conveyor belt or carousel as a function of the distance of the molds from fixed devices for filling, demolding and similar operations of the molds is carried out so as to provide control signals for the electric motor. The actual value is determined from a signal voltage generated in correspondence with the rotary movement of the electric motor. The signal voltage is additionally, and in parallel to the speed regulation, converted to electric pulses which are summed in their time sequence, as a function of the movement steps of the conveyor belt or carousel, and are compared with a predetermined master function which can be varied.

Abstract: An apparatus and method is disclosed for controlling motion of a tape dispensing apparatus or the like in response to both computer change in position signals and proportional and integral tracking error signals to maintain a desired conformal relationship between the tape dispensing apparatus and a contoured surface. The level of responsiveness to computer change in position signals versus tracking error signals is adjustable depending upon the severity of the contour so as to optimize servo tracking where necessary.

Abstract: A high speed machining controller comprises an acoustic emission sensor which is installed in or near a machine for machining a work piece in a high speed and which detects acoustic emission generated during machining a work piece; a signal processing means which is composed of a band-pass filter for passing an element of a frequency band corresponding to the acoustic emission by inputting a signal outputted from the acoustic emission sensor, a rectification circuit for rectifying a signal outputted from said band-pass filter, a peak detection circuit for detecting peak values of the signal outputted from the rectification circuit, and a smoothing circuit for smoothing output signals of said peak detection circuit and for outputting a signal corresponding to the amplitude of the acoustic emission for the purpose of processing the output signal of the acoustic emission sensor to detect its amplitude; a cutting condition discrimination means for judging the cutting condition of a work piece by comparing a detec

Abstract: A first set of parameters, including a preliminary cutting speed and a preliminary feed rate, is determined from the characteristics of the material to be cut, the cut to be made, the cutter, and the cutting machine. The hardness of the metal to be cut is coverted into Brinell hardness. The maximum allowable cutter force and a base cutting speed are calculated. The cutter force is the minimum of the maximum machine spindle side load and the forces required to: break the cutter at its shank, break the cutter at its flutes, and fracture the teeth. The maximum feed rate is calculated as the minimum of the maximum rates for: the desired surface finish, the maximum available horsepower, and the maximum force available. These calculation include correcting the maximum allowable cutter force and the maximum feed rate for fixture condition and machine condition and converting machine rate horsepower into spindle horsepower.

Abstract: A transport and stacker system in which the articles being transported are propelled in their path of travel by the moving magnetic field of a linear induction motor. The magnetic field also functions to attract the moving articles toward the linear motor and in order to overcome this attracting force and air bearing is provided. The air pressure acting against the attracting force is just sufficient to move the articles a slight distance away from the linear induction motor so that the articles move in the path of travel while suspended in air out of contact with the physical surface of the motor. When the desired position is reached, the article is dropped on a stack by deenergizing the magnetic field.

Abstract: A machine tool for machining a workpiece by feeding a cutting tool into the workpiece in a series of discrete steps wherein a constant value is stored for each of those steps, a calculation is performed responsive to the value of a variable factor affecting operation of the cutting tool, such as cutting tool diameter and/or workpiece material coefficient, to calculate for each of the discrete steps a feed value as a function of the corresponding constant value for that step and as a function of the value of that factor. Control means is provided for feeding the cutting tool into the workpiece as a function of the feed values thus calculated for a plurality of steps. Upon completion of feeding for any one step, the cutting tool is at least partially withdrawn from the workpiece and the cutting tool is subsequently feed into the workpiece as a function of the feed value of the next step.

Abstract: The present invention is intended to improve the machining accuracy of tracer control which moves a tracer head and a model relative to each other along a path specified by numerical information.Profile arithmetic means (4, 5, 30 to 33) creates a velocity signal (V.sub.a) in a tracing feed direction and a velocity signal (V.sub.z) in the Z direction on the basis of displacement signals (.epsilon..sub.x, .epsilon..sub.y, .epsilon..sub.z) from the tracer head (1) and direction signals (sin .alpha., cos .alpha.) indicating the tracing feed direction, which are supplied from direction signal generating means (36). Velocity signal generating means (18, 19) derives command pulse signals in the X and Y directions from numerical information indicating the path of travel of the tracer head (1) and the velocity signal (V.sub.a) in the tracing feed direction produced by the profile arithmetic means (4, 5, 30 to 33).

Abstract: A line tracking control method of controlling a robot (51) to cooperate with a conveyor (50) in its movement determines a speed of movement of the conveyor (50) as a constant, determines a corrective variable (d) based on the determined conveyor speed, finds a boundary value (B) for the speed of the conveyor (50), compares the boundary value with an actual speed of the conveyor (50), and adding or subtracting the corrective variable (D) based on the result of comparison, thus determining a command value for the robot.

Abstract: A system is provided for adaptively limiting the feed rate of a milling machine's positioning axes during a milling operation. Normal operation of the milling machine is controlled by a numerical control system (26). The invention utilizes strain gauges (18, 20) which sense loading force on the cutting tool during milling. A computer (24) is operatively connected to the strain gauges (18, 20). The computer is programmed to receive signals from the strain gauges and to use such signals to automatically override the programmed feed rate in the numerical control system (20), to maintain a specified peak side load on the cutting tool.

Abstract: A numerically controlled working process for a machine tool or the like is improved by reducing the idle time of the tool. This is effected by inputting the preworking shape of the workpiece and comparing this shape with a tool path determined on the basis of the desired finished shape. When the working path of the tool passes through an area where no machining takes place (the workpiece, for example, being precut in this area) the tool is made to move at a relatively high speed to the next actual machining location.

Abstract: A microtome has a specimen holder which executes a vertical up and down movement relative to a cutting knife and which has a guide mechanism in which a sleeve is arranged so as to be horizontally displaceable. The sleeve is provided at its front end with a specimen clamping mechanism and in its interior with a micrometer nut which is secured against axial displacement and through which extends a micrometer spindle mounted on the guide mechanism. The micrometer nut has on its outer face a toothed ring which is connected operatively to a pinion connected to an electric motor. When the electric motor is activated the sleeve is displaced in the guide mechanism. The micrometer spindle extends, on the side opposite the specimen clamping mechanism, through the guide mechanism as a stub end on which is located a mechanical cutting-thickness advance mechanism.

Abstract: Cutting time and wear of the cutter is reduced for copy-cutting of a workpiece by tracing a concavity of a model with a stylus. The clamp level is changed in sequence and, at each clamp level, contour tracing along the entire circumference of the inner wall of the concavity of the model, and X-Y plane tracing for cutting the part above the clamp level that is left uncut by the contour tracing, are carried out.

Abstract: A method and control system for gear cutting machines such as hobbing equipment, shaper cutters and bevel-cutting equipment for achieving greater accuracy, productivity, and gears of increased quality while eliminating error, tedious calculations, labor and product variation is provided by employing a control system and utilizing a method of gear cutting wherein optimum cutter efficiency is maintained by electronically monitoring and controlling cutter input power, cutter shift and workpiece feed or in an alternative embodiment by varying index drive and feed drive in response to inputs measured from the cutter or cutter motor to produce gears approaching the optimum theoretical calculated configuration.

Abstract: A tapping machining method for moving a tapping tool to a commanded position in synchronism with rotation of a spindle, to subject a workpiece to threading, and thereafter rotating the spindle in the reverse direction and withdrawing the tapping tool from the workpiece in synchronism with rotation of the spindle. The steps of the tapping machining method include moving and positioning a spindle, namely the tapping tool (4), from an initial point (Pi) to an approach point (Pr) in the depth direction (along the Z axis) while being rotated at a constant velocity. Then a pulse distribution calculation is started by using the pitch of a screw and pulses of a frequency proportional to the rotational velocity of the spindle, and threading is performed while the tapping tool is moved toward a target position (Pe) by the distributed pulses.

Abstract: In a control circuit for a transfer device including feed bars movable along two or three axes and servo-actuators respectively provided for driving the feed bars in stroke-forming movements along the axes, there are provided a stroke signal generator for generating a stroke defining signal separately from press movement and press control device for controlling the operation of a press. Based on the output signal from the stroke signal generator, the press control delivers press starting and stopping instructions at appropriate instants not interfere with the movements of the feed bars for initiating press operations of an intermittent nature.

Abstract: A turning machine is characterized by a new and improved control and mechanism for positioning the turning tool on the head. A CNC control issues command signals for selectively positioning the tool on the head. These signals are developed from an encoder which provides the instantaneous position of the rotating part being turned and from a program in the CNC containing information about the part. A closed loop control system receives these command signals and converts same into a control current for a linear motor which is the prime mover controlling the positioning of the tool on the head. The linear motor operates a carriage on the head and the cutting tool mounts on the carriage opposite the connection of the linear motor to the carriage. The carriage is a hollow bar guided on the head by sets of rollers which are cooperatively arranged to provide yieldably forceful constraint of the bar.

Abstract: In a machine tool, the tool is moved using a signal representing a required profile of the surface being machined. This signal is fed to a transducer, such as a piezoelectric crystal or a D.C. linear motor, which converts the signal into a corresponding linear movement which is transmitted to the tool. The tool can also be vibrated ultrasonically during machining. Such machines can be used for producing workpieces which are non-circular in cross-section and/or which are barrelled or tapered along their length.

Abstract: The present invention is intended to prevent a cutter from biting into a workpiece at a point of a sudden change in the configuration of a model in tracer control equipment. Sampling circuits (12, 12X to 12Z) respectively sample a composite displacement signal and displacement signals in the X-axis to Z-axis directions at equal time intervals. An arithmetic circuit (17) obtains the angle between the displacement vector of a stylus (1) at the current sampling and the displacement vector of the stylus (1) at the previous sampling from the sample values by the sampling circuits (12, 12X to 12Z). A comparator (18) compares the result of calculation by the arithmetic circuit (17) and a reference level and, according to the result of comparison, controls whether to decrease the feed rate. Accordingly, the cutter can be prevented from biting into the workpiece at the sudden-change point in the configuration of a model.

Abstract: A machine tool is provided with a controller for computing, as a function of an established radius and a preset feedrate, a rotational speed for rotating the machine spindle to provide a uniform surface speed at the working edge of a tool as the tool alternates between linear movement along an X and/or Y axis and arcuate movement along the C-axis of the spindle. A method is provided for gauging straight surfaces and adjoining arcs at a constant feedrate without interruption.

Abstract: A motor 12 (FIG. 2) is controlled to move at a demanded velocity, input at 29, by sampling the position of the motor at sample intervals, digitally determining the demanded change in position per sample interval, modifying each position sample by the addition of said demanded change, comparing the modified position value with the previous modified sample to derive a position error signal representing the position error between the instantaneous position and that demanded by motion at the demanded velocity, and applying the position error signals from successive sample intervals to motor drive means.

Abstract: Method and apparatus for moving a workpiece and/or a tool to various locations in a three-dimensional space to perform operations on the workpiece wherein a micro-computer numeric control system is used to provide a multi-axis motion control system using DC electric servo motors, each of which responds to its own control system to operate mechanisms which cooperate to perform the desired operations on the workpiece.

Abstract: The load current of a spindle motor adapted to drive the tool of a numerical control machining apparatus or a feed motor adapted to move a machining table on which a workpiece is placed is detected during machining, the detection signal is applied to the input unit of a numerical control device to obtain the load output, and the load output is compared with an allowable value, so that the comparison signal is utilized to control the feed speed of the feed motor adapted to move the machining table of the apparatus or to output an alarm signal.

Abstract: A plurality of path patterns (MCR.sub.1 -MCR.sub.3), in which at least data specifying tracing areas serve as variables, are registered in a memory (102) beforehand, tracer machining data including call instructions (MCC.sub.1 -MCC.sub.3) for calling a predetermined path pattern, as well as actual numbers, are stored in a memory (101) in advance, and tracer machining data are read block-by-block to perform tracer control. When a path pattern call instruction is read, the predetermined path pattern is read out of the memory (102), the variables are replaced by actual numbers to obtain a tracing area, and tracing is performed in the tracing area on the basis of the read path pattern.

Abstract: First and second tool control blocks respectively precede and follow a corner on a tool path. A pulse distribution computation based on NC command data in the second block is not executed at the instant that a pulse distribution computation based on NC command data in the first block ends. Rather, a pulse distribution computation based on the NC command data in the second block is performed starting at the instant that a feed speed based on the NC command data in the first block is reduced to a prescribed speed by being decelerated. As a result, the torch of a gas cutting machine or the like will cut the corner portion quickly with a high degree of accuracy and without cutting the corner to an overly rounded shape.

Abstract: According to the present invention, a control system is provided for advancing and retracting the knife and pressure bar carriage of a veneer slicer. This system replaces the conventional feed screw carriage actuator and permits the knife and pressure bar tilt mechanism to be eliminated. The control system includes a hydraulic linear actuator for incrementally advancing and retracting the carriage and a programmable linear motion controller for controlling the sequence in which the linear actuator advances and retracts the carriage and the distance which the linear actuator advances and retracts the carriage. The controller includes a memory into which a program is loaded. The program determines the sequence, direction and distance that the linear actuator advances and retracts the carriage.

Abstract: A machine present position region discrimination method divides a stroke, over which a movable portion of a machine travels along a single controlled axis, into n equal parts to partition the stroke into regions, each region having a length I. A region number is assigned to each region sequentially from one end of the stroke to the other. A present position region number A is incremented or decremented in dependence upon the travelling direction when an accumulated travelling distance B of the movable portion of the machine exceeds the region interval length I (during movement in the positive direction), or is less than zero (during movement in the negative direction). The resulting present position region number A, which is indicative of the present position region of the movable portion of the machine, is supplied by an NC unit in which the present position region number A is calculated to the controlled machine.

Abstract: A technique of determining the distribution of pulses along two perpendicular X-Y axes of a numerically controlled machine can be used for linear, circular, and parabolic interpolations and may be extended to computer graphics. At the initial point on the curve and at each succeeding point, a decision is made to increment the X axis, the Y axis, or both axes. This decision is based on a deviation index which is an index of closeness to the desired curve. Hardware is minimized and involves only additions, compares, shifts, and increments/decrements.

Abstract: In a feed control system, a feed controller controls a servomotor in such a manner as to reduce the difference between an objective position and a present position of a movable body. An interference detection circuit coupled to the feed controller detects the occurrence of an interference between the movable body and an obstruction when feed movement of the movable body is discontinued nevertheless the difference between the objection and present positions does not reach zero. A digital computer is coupled to an objective position counter provided in the feed controller to selectively set therein objective positions to which the movable body is to be positioned successively. The digital computer, when receiving a signal from the interference detection circuit, sets the objective position counter with data for moving the movable body a predetermined amount in a direction opposite to that wherein the movable body was moved before the occurrence of an interference.

Abstract: The present invention provides a high response inexpensive microprocessor based control system. The system uses only one detector that detects only one motion characteristic of the object controlled by the system. In the preferred embodiment, the system controls the position and velocity of the movable member of the motor by creating commands that represent the desired position of the movable member 1024 times per second. The system also provides methods for improving the accuracy and precision of the system.

Abstract: A system for finely feeding a movable member being movable relative to a stationary member.This fine feed system is constructed such that the movable member is provided with a fine feed mechanism, which includes a screwshaft and a nut member threadably coupled to the screwshaft and capable of being suitably clamped against the stationary member. A control device is provided for causing a driving motor to drive the screwshaft on condition that a detector to regulate the relatively movable range between the screwshaft and the nut member is not in operation, while, for causing the driving motor to operate so that the screwshaft and the nut member can return to original relative positions, on condition that the nut member is not clamped against the stationary member. The fine feed of the movable member can be instantaneously performed no matter where the movable member may be in its movable range.

Abstract: A system in which the radius of a tool is compensated for in the three-dimensional machining of a workpiece, wherein a tool is offset from a commanded tool path by a distance commensurate with the tool radius.

Abstract: The present invention increases screw cutting accuracy and simplifies the control of a screw cutting control system which performs screw cutting through the use of a numerically-controlled machine tool. A tapper (TPP) connected to a spindle, holds a tap (TAP) in a manner to be movable in the axial direction of the spindle, transmits the rotation of the spindle to the tap (TAP) for a predetermined range of forward axial movement of the tap (TAP) and transmits the rotation of the spindle to the tap (TAP) when the spindle is reversed. During screw cutting, feed by a feed motor (SZ) stops after the tap (TAP) enters a workpiece and the screw cutting is effected by the thrust of the tap itself resulting from the rotation of the spindle. The sequence of screw cutting is commanded by one block of command data.

Abstract: A method and an apparatus for controlling spindle speed are disclosed. When the speed ranges of respective gear ranges are selected in advance so that speed ranges corresponding to neighboring gear ranges partially overlap one another, and the gear range conforming to the commanded spindle speed is selected for rotating the spindle at the commanded spindle speed, it is determined whether the commanded spindle speed belongs to the currently selected range, no gear change is made if the decision is affirmative, and the gear range to which the newly commanded spindle speed belongs is found if the decision is negative, the gear range being switched to the gear range thus found.

Abstract: A pen-lift system is provided which can achieve high speed plotting while maintaining line definition of drafting quality. The system includes a pen-lift mechanism for raising and lowering the pen, a pressure control system in order to provide a constant pen force for different kinds of pens, a velocity controller for varying the vertical velocity of the pen in response to changes in platen height and relative lateral pen position, and a position controller for sensing the present pen height relative to the platen and for actuating the pen-lift mechanism to achieve the desired pen-lift heights for different plotting situations.

Abstract: A workpiece transfer bar is reciprocated by a rack driven by a pinion which is driven by a servomotor through an eccentric arm. A computer is used to set rates of acceleration and deceleration, a maximum speed, etc. in accordance with the origin of the transfer bar, stroke thereof etc.

Abstract: An acceleration/deceleration circuit for raising or lowering a feed velocity, in order to achieve a commanded velocity, over a prescribed time constant irrespective of the magnitude of a change in velocity. The acceleration/deceleration circuit includes means (301) for computing a traveling distance along each axis every sampling period (T), a first storage section (#1 through #n) for storing n samplings of traveling distance components along each axis, a second storage section SUM for storing results of computation, and an arithmetic section (ADD, ACC, DIV) for performing an operation:.sub..DELTA. Xn-.sub..DELTA. Xo+St.fwdarw.Stwhere .sub..DELTA. Xn represents the latest sampled traveling distance component, .sub..DELTA.

Abstract: A jig grinder is provided with a controller for computing, as a function of an established radius and a preset feedrate, a rotational speed for rotating the machine spindle to provide a uniform surface speed at the cutting edge of the grinding tool as the tool alternates between linear grinding with an X and/or Y axis and arc grinding along the C-axis of the spindle. A method is provided for grinding straight surfaces and adjoining arcs at a constant feedrate without interruption.

Abstract: A numerical control method for executing numerical control processing using a numerical control unit (102), based on a machining program having plural items of command data recorded on an NC tape (101). Under the numerical control method, numerical control processing is executed based on a succeeding item of command data which has been preread or which has been read after completion of numerical control processing based on an item of preceding command data. An upper limit feed speed (V.sub.L, V.sub.C), based on a workpiece shape commanded by the machining program and on an allowable machining error, is previously determined and stored in registers (RG1, RG2). The magnitude of the upper limit feed speed (V.sub.L, V.sub.C) and the magnitude of an actual feed speed (Vi) is compared, and the actual feed speed is clamped to the upper limit feed speed V.sub.L, V.sub.C, even when Vi exceeds V.sub.L or V.sub.C.

Abstract: A speed control apparatus according to the present invention includes a pulse generator for generating a number of pulses proportional to an angle of rotation of a servomotor, a speed signal generator for converting the frequency of the pulses into a voltage indicative of an actual speed of the servomotor in order to feed back the voltage through negative feedback, a detector for detecting reversal of the direction of rotation of the servomotor, a positional change detector for detecting the change in a position of the servomotor after the reversal of the direction of rotation of the servomotor by counting the pulses produced by the pulse generator, and a circuit for lowering the voltage indicative of an actual speed until the position of the servomotor has changed beyond a predetermined amount.

Abstract: A method and apparatus for automatically adjusting an operation time of a servosystem into a predetermined allowable range, either from the outside or from the inside. An average operation time of the servosystem is calculated and then an amount of level shift is calculated from the resulting average operation time. Based on the resulting level shift, the operation time of the servosystem is stepwisely shifted at a given time interval. After the shift, an average operation time of the servosystem is calculated again. This is repeated until the average operation time enters the allowable range.

Abstract: Mounting a position sensor equipped planar armature, in operative juxtaposition to a stator, by a spring colonnade basket of flexure columns, provides a low-friction precision X-Y-Theta positioner which has computer control of operations with feedback of actual position for closed loop servo operation.The spring colonnade basket provides freedom of motion in the X, Y and Theta (rotation about an axis mutually perpendicular to X and Y) dimensions without static friction present in sliding or rolling motions. The armature, which carries a gripper or other end effector and is free to move only within its own plane, is positioned by a motor made up of the armature and a stator mounted on a support platform. The stator is made up of a pair of U-shaped permanent magnets, each having U-shaped pole pieces mounted orthogonally to each other, at 45 degree angles to the axis of the magnet, so that each electromagnet controls motive power in both X and Y dimensions.

Abstract: A numerically controlled machine tool comprises a tool movable into engagement with a workpiece, means for generating a first signal being a measure of the distance between the tool and a datum surface provided on a relatively fixed part of the machine, a first closed loop system adapted to move the tool toward the workpiece and having the first signal as feedback, means for generating a second signal being a measure of the distance between the tool and the workpiece, a second closed loop system (33) having the second signal as feedback, and means responsive to the second-mentioned distance attaining a threshold value, while being moved under the control of the first system, for changing control of the tool movement from the first to the second system.