Abstract: A method and apparatus for sensing the present position of a movable machine element in a position control system when a position control loop in the system is placed in the open state. In the position control system, error storage means computes and stores an error which corresponds to the difference between a command value produced by a control unit and an amount of movement sensed by a position sensor provided on a motor shaft or on the movable machine element. A speed control circuit controls the motor in accordance with the error from the error storage means.

Abstract: A method and apparatus for sensing the current position of a movable element in a position control system which includes first and second control devices each having a command pulse generating means and error storage means for computing and storing an error between a number of command pulses and a number of feedback pulses indicative of an amount of motor movement. The position control system also includes a speed control circuit for driving and controlling the motor on the basis of the error in the storage means, and a switching circuit for selectively connecting the first and second control devices to the speed control circuit, the current position of the movable element being sensed by one control device when the other control device is connected to the speed control circuit.

Abstract: The direction of pick feed is determined by a feed-direction signal produced based on the result of decision by a phase decision circuit and the direction of pick feed inputted from an input unit, and the pick feed is effected by a contour trace. In the case of tracing a hemispherical model, the pick feed can be achieved in a plane parallel to the X-Y plane. The feed-direction signal indicates whether the direction of tangential velocity is to be +90.degree. or -90.degree. with respect to the normal direction. A velocity arithmetic circuit inverts the polarity of its output, a tangential-direction velocity signal, depending on the binary value of the feed-direction signal. Motors are driven by the outputs from amplifiers selected by a gate circuit, by which, in the case of tracing the hemispherical model, the pick feed plane is made to correspond to that in the case of a contour trace, wherein the pick feed can be effected in a plane parallel to the X-Y plane.

Abstract: A clamping tracer control system which performs a tracing feed and a pick feed alternately and effects a clamping feed at a preset clamp level and in which, between the pick feed position where the clamping feed is carried out first and the pick feed position where the clamping feed has been completed, tracer control is repeated while changing the clamp level sequentially, and when the clamping feed has been completed in the repeated tracer control, the clamp level is restored to its area of initial value to resume tracer control of the tracing feed and the pick feed alternately in the next area.

Abstract: In a system which performs tracer control by calculating the direction and velocity of tracing using signals from a tracer head tracing the model surface, there are provided an input unit for entering data defining the tracing operation, a memory for storing the data and a processor for reading out the data from the memory to control respective parts of a control device. Of the data defining the tracing operation, stored in the memory, data concerning the reference displacement of the tracer head is read out by the processor to change the reference displacement for each profile modeling operation, thereby automatically performing repetitive tracing.

Abstract: A three-dimensional tracer control system which is provided with an integration circuit for integrating the difference between a Z-axis direction displacement signal and a reference displacement signal and an adder for adding together the above-mentioned difference and the output from the integration circuit. The trace velocity in the Z-axis direction is controlled by the output from the adder, by which it is possible to perform tracing, with the Z-axis direction displacement signal and the reference displacement signal held nearly equal to each other; consequently, machining accuracy is increased.

Abstract: A tracer control system which performs tracer control based on a displacement signal from a tracer head tracing the surface of a model and is equipped with the function of freely setting the infeed of a cutter for machining a workpiece. The tracer control system is provided with a first drive system for feeding the tracer head in the Z-axis direction, a second drive system for feeding the cutter head in the Z-axis direction, first and second position detectors for detecting the positions of the tracer head and the cutter head in the Z-axis direction, and a superimposing circuit for superimposing on each other a position detection signal from the first position detector and an infeed command signal for setting the infeed of the cutter head. The cutter head is fed by the second drive system in the Z-axis direction so that the difference between output signals from the superimposing circuit and the second position detector may be reduced to zero.

Abstract: In a tracer control system which controls tracing based on displacement signals from a tracer head tracing the surface of a model, there are provided position detectors for detecting the positions of a tracing machine along the X, Y and Z axes and angle correcting means. The difference between a set trace direction and the actual trace direction detected by the position detectors is obtained for every other fixed distance of movement along the X-axis or Y-axis direction and a trace velocity along the X-axis or Y-axis direction is corrected by the angle correcting means so that the above difference may be reduced to zero, thereby controlling tracing to be performed in the set trace direction.

Abstract: In a tracer control equipment which calculates a trace direction and a trace velocity using signals from a tracer head tracing the model surface and performs tracer control in accordance with the calculation results, there are provided a memory for storing numerical command data and means for reading out the numerical command data by a processor from the memory, whereby to add a numerical control function for positioning control to the tracer control equipment.

Abstract: During a tracing operation of a tracer head for detecting the surface configuration of a model, the current position of the tracer head in the Z-axis direction is detected and a maximum value of the detected tracer head positions is stored in a memory means. When the tracer head is returned from a trace terminating end to a trace starting end, it is quickly returned to a position corresponding to the sum of the stored maximum value and a constant value.

Abstract: Data for determining a limit value of the trace range of a model are stored in a memory and the stored data are read out therefrom by a processor to calculate the limit value of the trace range. The current position of a movable machine part is detected and compared with the limit value and when it is detected by the processor that the current position of the movable machine part has reached the limit value, a trace feed is switched to a pick feed. After the pick feed is performed a predetermined distance, it is switched again to the trace feed. A desired trace range is set to achieve tracer control without the provision of limit switches.

Abstract: An input signal is written in n memory elements one after another in accordance with clock pulses, the contents of the n memory elements are added together by an adder, and the added output from the adder is divided by n in a divider, thereby converting an input signal having an abrupt change to a signal having a gentle change.

Abstract: In one forward or backward trace path on a model, a jerk point in the surface configuration of the model is detected and the position of the jerk point is stored in a memory. The reduction of the trace velocity is started a predetermined distance short of the stored position of the jerk point in the trace direction and when a jerk point is detected again, the position of the jerk point previously stored in the memory is updated and the reduction of the trace velocity is released, thus achieving high accuracy trace.

Abstract: In a tracer control system, parameters necessary for a trace operation, such as, for example, tracer head reference displacement value, trace axis, trace direction, pick feed value, and various limits, are set in combination for each trace mode. A character display is provided for displaying various parameters, so that it is easy to confirm each of the required parameters corresponding to a selected trace mode, and check whether the setting of all required parameters has been completed or not and whether the value of each set parameter is the desired one or not.

Abstract: In a system which performs tracer control by calculating the direction and the velocity of tracing through utilization of signals from a tracer head tracing the model surface, there are provided an input unit for entering data defining the tracing operation, a memory for storing the data and processor for reading out the data from the memory to control respective parts of a control device. Data concerning clamp tracing is read out by the processor to change the clamp level by a predetermined value for each working, thereby performing repetitive clamp tracing.

Abstract: In a system which performs tracer control through the use of a displacement signal of a tracer head tracing the surface of a model, there is provided: a first coordinate conversion circuit in which signals representative of the cosine and sine of the azimuth angle of the feed axis in the X-Y plane of a mechanical coordinate system and X- and Y-axis displacement signals of the tracer head are respectively multiplied by multipliers and the output signals from the multipliers are added together to thereby obtain a displacement component signal of the feed axis; and a second coordinate conversion circuit in which a signal for controlling the feed rate in the feed axis and the signals representative of the cosine and sine of the azimuth angle of the feed axis are respectively multiplied by multipliers to obtain feed rates along the X- and the Y-axis.

Abstract: In a system which calculates a digital quantity at known time intervals and converts the calculated result to analog form to apply a command, for example, to a numerical-controlled machine tool, there is provided a circuit which obtains a difference value between current and previous calculated results and outputs a value obtained by dividing the difference value by N, and an adder which adds the output from the dividing circuit to the previous calculated result at time intervals of 1/N of the known time interval. The added result by the adder is converted to analog form at time intervals of 1/N of the known time interval to issue the command; as a consequence, the command does not change abruptly but undergoes a smooth change, eliminating the possibility of a great shock being imparted to controlled equipment, for example, a numerical-controlled machine tool.

Abstract: The present invention provides porous polytetrafluoroethylene ("PTFE") products having fine pores and high porosity, the pore diameter being less than about 1,500A, generally ranging from about 100A to 1,000A. The process for the manufacture of these products comprises: (a) shaping of a lubricated PTFE mixture, by extrusion and/or rolling; (b) a first stretching of the shaped mass while in an unsintered state; (c) free sintering of the stretched mass at a temperature above 327.degree. C; and (d) a second stretching of the sintered mass. These porous PTFE products are suitable for use as gas separators, diaphragms, filters, and other applications.