JPH0287905A - Device for controlling linear motor - Google Patents

Abstract

PURPOSE: To suppress fluctuation and hammering by receiving a speed signal and a distance signal, respectively, from a speed measuring circuit and a distance measuring circuit and employing these signals along with other desired logical inputs for energination control of a stator element thereby driving a movable element with a short thrust. CONSTITUTION: Output voltage signal from a pulse encoder is delivered to an encoder regulation unit 36 thence to a comparator 38 for comparing the period of an encoder pulse with the duration of pulse generated from a reference voltage generating means 40. If the duration of the reference voltage pulse is shorter than the period of the encoder voltage pulse and the shuttle speed is low, output from an error signal element 42 triggers a minimum on time element 44 to produce a holding signal otherwise output from the error signal element 42 is transmitted to an output driver element 46 thence to a programmable controller. On the other hand, output voltage from the pulse encoder is delivered to a binary counter 48 and the output therefrom is delivered, along with the output from a binary reference element 52, to a binary comparator 50. Output from the comparator 50 is received by an output driver 54 which delivers a distance signal to the programmable controller.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides improvements in the speed control of linear electric motors;
More particularly, it relates to an improved apparatus and method for controlling the energization of multiple linear motor stators employed to drive a common reactor.

Although multiple linear motor stators or thrusters are used to drive the common r+] dynamic element f or the actuator, conventional methods of controlling stator energization have drawbacks.

A typical on-off type control responsive to the speed of the moving element is performed when the speed request signal occurs during acceleration of the moving element or when the velocity of the moving element falls below a desired value. Regardless of whether this occurs, all stators are energized during the speed demand signal, so that the movable element r- is driven with a short thrust, causing fluctuations and hammering.

Thrust modification control is used in which the thrust produced by the stator is adjusted using appropriate speed sensing circuitry to control the thyristors and thyristors that adjust the applied voltage. However, this method is expensive and complex.

Although variable frequency type control is possible, it is not suitable at low speeds of the moving member because the minimum spacing between the electrode faces of the linear motor stator is mechanically limited.

Control problems when multiple stators are employed to drive a common actor are further complicated if the actors drive i+J variable loads.

In the control of the present invention in a linear motor having a movable reactor element and one or more electrically energizable stator elements, an encoder device driven by a dynamic element f is employed to generate a pulsed output voltage. , the period of each encoder voltage pulse is proportional to the speed of the moving element, and the number of encoder voltage pulses is proportional to the distance traveled by the moving element. The pulse encoder output voltage is supplied to a speed measurement circuit and a distance measurement circuit.

Essentially, the speed measurement circuit generates a reference voltage pulse of duration Vr proportional to the desired speed of the moving element in response to each encoder voltage pulse, and defines the period of the encoder voltage pulse as the duration of the reference voltage pulse. and generates A-1 and de-energize speed signals in response to the reference voltage pulse having a duration less than and greater than the period of the encoder voltage pulse. This basic configuration can be provided in two locations to provide speed voltages for different desired speeds.

The distance velocity circuit counts the number of encoder voltage pulses and compares this number with a reference number representing the desired distance of movement of the moving element, 2
generate a distance signal in response to a match between the two numbers. also,
This configuration can be provided in two locations to provide speed voltages for different desired speeds.

The programmable controller receives speed signals from the speed measurement circuit, distance signals from the distance measurement, and employs these signals as well as other desired logic inputs to control energization of the stator elements. In an embodiment of the invention, the movable element is a shuttle with a reciprocating capacity of 1jJ driven by a plurality of stator elements during forward and backward movement between a return station and an advance station, which is a shuttle with a reciprocating capacity of 1jJ, which is driven by a plurality of working stator elements. are employed to advance varying numbers of article carriers through the carrier. The speed signal input to the programmable controller includes a first speed signal indicative of the speed of the movable element relative to a desired maximum speed of forward motion of the movable part r;
a second velocity signal indicative of the velocity of the movable element relative to a desired maximum velocity of the return movement of the movable element; and a third velocity signal indicative of the velocity of the movable element relative to a desired creep velocity in the terminal portion of the forward or return movement. The distance circuit signal input to the programmable controller is 11 from the return position.
It includes a first distance signal indicative of a desired distance of movement of the movable element to a deceleration point of the 11-decimal motion, and a second distance signal indicative of a desired distance of movement of the movable element to the deceleration point of the return movement. Other logic inputs to the programmable controller include a signal indicating that the movable element is in the return position, a signal indicating that the movable element is in the forward position, and a signal indicating the number of article carriers at the work station.

These various signal inputs are utilized by the programmable controller logic in the following manner.

■ In response to the return position signal and also in response to an external command, the stator element 1i! In response to the speed signal, the movable elements are progressively energized at appropriate time intervals until maximum forward speed is achieved. The number of stator elements energized is limited by the number of article carriers being propelled.

2. In response to the first distance signal, the stator end is urged backward gradually at appropriate time intervals to decelerate the movable element. Then, in response to the third creep speed signal, the stator element's backward biasing is interrupted and its limited advance biasing is interrupted as required to maintain the movable element at the creep speed until the forward position signal is received. strength will be restored.

Control of the return movement of the iiJ dynamic element is accomplished in the same manner, but in response to the second degree velocity and distance signals.

Another preferred feature is that the programmable controller includes ring counter logic that, in response to completion of a forward-return movement cycle by the movable element,
Rotating or changing the sequence of progressively energizing the stator elements in a forward-return motion cycle. This distributes the cropping load to the stator elements and reduces heat generation by the stator elements.
Limit absorption.

Other features and advantages of the invention will become apparent from the following description of an embodiment, which is illustrated in the accompanying drawings.

In FIG. 1, a reciprocating shear/tortle 10 is a joint for a plurality of linear motor stators arranged in groups A, B, and C on both sides of the shuttlecock 10 and driving the shuttlecock 10 in forward and return motions. Form a street actor.

The shuttlecock 10 is employed to advance the article carrier 12 through successive work stations 5TAI to STA4, the forward and backward movement of the shuttlecock 10 being substantially equal to the distance from one work station to the next. The conveyor indicated by the dashed line 14 is the cow Yariya 12
is propelled to STA 1 and carrier 12 is picked up by 5TA4, and each stationcon includes a stop device 16 for positioning the carrier.

Details of a typical mechanism for this type of construction are provided in U.S. Pat.
No. 4.706, incorporated herein by reference.

Another shuttle structure of this general type is U.S. Patent No. 4.66.
No. 9.388, which is also referred to herein. Generally, in these configurations, the reactor portion of the shuttle consists of an aluminum beam movably mounted between a pair of opposing stators 18 forming one of the LIM groups. A suitable mechanism is carried on the shuttlecock for engaging and propelling the carrier 12 on forward motion of the shuttlecock, and disengages from the carrier on return motion of the shuttlecock.

The control system of FIG. 1 includes a programmable logic controller 20 that regulates the firing of a conventional solid state relay (not shown) with the following input signals to energize the stator 18 of the LIM group.

1. Return or load position signal from limit switch 22 activated by shirttle IO; 2. Shitletle I
Advance or no-load position signal from limit switch 24 actuated by O: 3, Carrier in, carrier out signal from limit switch 26, respectively 28 actuated by carrier: 4 Velocity measurements shown in FIG. Speed signals vl, v2 . from circuit 30; V3: and 5, the distance signal D1. from the distance measuring circuit 32 shown in FIG. The D2° speed and distance signals are derived in part from encoder means 34, which includes a rotatable wheel frictionally driven by the shuttlecock IO, which generates a pulsed output voltage in response to movement of the shuttlecock IO. do. The period of each voltage pulse is proportional to the speed of the shuttle 10;
The number of output voltage Hals is proportional to the distance traveled by the shuttle IO. This output voltage is supplied to a speed and distance measurement circuit described below.

The speed measuring circuit in FIG. 2 shows the speed signal v1. Circuit elements required for v2 or v3 are schematically shown. The pulse encoder output voltage signal is sent to an encoder yssq unit 36, such as a high gain subrift Darlington opto-isolator, which filters out unwanted electrical noise or transient signals and provides a clean pulse encoder output voltage signal. This encoder output voltage is supplied to an enfuder period comparator 38, which is a dual-stable multivibrator. The first section of comparator 38 generates a constant short negative delay pulse at each positive transition of the encoder pulse to move the logic test away from the time zero reference and reduce spurious results. The second section of comparator 38 is triggered to generate a reference voltage pulse having a duration proportional to the desired speed, the duration being R
It is determined by voltage setting means in the form of a C circuit 40. The circuit preferably consists of a plurality of resistors of different values that can be selectively connected by switches in parallel with the capacitor, the duration of the reference voltage pulse being equal to the product of the ohmic number of the resistor and the 7 Arad number of the capacitor. Alternatively, the R6 circuit may be of the type shown by circuit 40A in FIG. 5, which may be modified as desired.

The duration of the reference voltage pulse is compared to the period of the encoder voltage pulse, and depending on whether the duration of the reference voltage pulse is smaller or larger than the period of the encoder voltage pulse, an error signal element 42, which is a flip-flop circuit, is energized. or generate a deactivation signal.

If the reference voltage pulse duration is less than the encoder voltage pulse period, indicating that the speed of the shuttle torque IO is low and that a speed energization signal is required, the output of error signal element 42 is
on time) element 44 to generate a hold signal on the next encoder pulse.

Element 44 can be a monostable multivibrator similar to comparator 38. The hold signal inhibits the deceleration signal for a minimum period of time at least equal to the time required to energize one of the LIMs.

If the reference voltage pulse duration is greater than the encoder voltage pulse period, indicating a high shuttle speed and a need for a deceleration signal, the output of error signal element 42 has no effect on minimum-on-time element 44; It is transmitted to an output driver element 46, which can be a dicoal NAND buffer/driver.

Driver element 46 generates an on or off signal that is provided to programmable controller 20.

It will be appreciated that the speed board shown in FIG. 1 includes the speed measurement circuitry described above for each speed output Vl, V2. The output Vl is an on or off signal, and the shuttle 1
A speed of 0 indicates that the speed is less than or greater than the maximum desired speed during forward motion. Output (3) is an on or off signal, indicating that the speed of the shuttlecock IO is less than or more than the maximum desired speed during the return movement. Output v2 is an on or off signal indicating that the velocity of shuttlecock 1o is lower or higher than the desired creep velocity at the terminal portion of the forward or return movement.

The encoder voltage pulses (which can be sized according to the desired resolution) are sent to a ripple carry binary counter that advances one count on each negative transition. A binary comparator 50, such as a multi-bit magnitude comparator, is connected to a set of inputs receiving the output from the counter 48 and a toggle switch represented by a binary reference element 52 and establishing a pulse value or count. and another set of inputs. When the counted pulse force is equal to or exceeds the reference value, the output of the comparator 5o changes from low to high and is accepted by the output driver 54;
This output driver is a non-inverting buffer and provides a distance signal to the programmable controller.

Two such distance measuring circuits are employed in the distance board of FIG. One circuit generates a Dl output signal when the distance traveled by the shuttlecock IO from the return position in forward motion is equal to the distance to the desired deceleration point. The second circuit generates a D2 output signal when the distance traveled by the shuttlecock 10 from the forward position on the return motion is equal to the distance to the desired deceleration point.

Programmable Logic Controller The programmable logic controller software gates outputs that control the firing of solid state relays that energize LrM groups A, B, and C of FIG. The logic gate action of these outputs is load or return position limit switch 22, no load or t'f; Outputs Vl, V2. V3 and the output DI from the distance measurement circuit
, based on D2. The logic also determines the firing sequence of LIMli, the maximum number of LIM groups, and this maximum number L r M
Determine gradual or gradual activation of groups.

The sequence of the forward indexing movement of the shirttle IO is 3A,
Shown in 3B and 4A. Return by the shuttlecock 10 or engagement of the load position limit switch 22 indicates that a forward movement can be performed, which is initiated by a transfer permission signal (FIG. 1) to the programmable controller 20. The forward contactor is energized and the LIM group is progressively accelerated at appropriate time intervals necessary to accelerate the shuttlecock 10 to a speed Vl and maintain the shuttlecock at that speed until the deceleration point is reached and the DI difference signal is generated. loaded. The DI difference signal causes the backward movement contactor to be energized, and the 11M group is gradually energized backward at appropriate time intervals, and the shuttlecock 10 is finally decelerated to the creep speed v2, which causes the controller to move the distance 111D.
Calculate 3. At distance fiD3, the retreating contactor is deenergized and the forward contactor is energized to reduce the creep rate to human power v2.
is maintained by the modification until the shuttlecock 10 activates the no-load or advance limit switch 24, deenergizing the advance contactor and completing the forward indexing motion.

The return indexing motion sequence is similar, except that the 1,1M group is gradually energized in an appropriate time sequence to accelerate the shirt torque 10 to speed 3, and the shuttle torque continues until the D2 manual force is removed. is maintained at that speed by the modification of manual ■3, and the energization of the LIM group is reversed to generate the shuttle torque I.
The purpose is to decelerate O to the creep velocity v2. The creep speed is maintained by modifying the human power ■2, and finally the shuttle 10 activates the load or return position switch 22,
Deenergize the retracting contactor to complete the return indexing movement.

FIG. 3B shows the combined time and carrier count logic employed to progressively energize the LIMs in response to the speed-on signal. If the velocity signal is still true for 40 seconds after the -order L1M group is energized, then the second L, +
The M group is activated if the carrier 12 count is greater than 1, and if the velocity signal is still true for 60 seconds after the next LIM group is activated, the third LIM group is activated when the carrier 12 count is greater than 1. It is energized when it is greater than 2. When the speed signal is turned off, all energized LIM groups are deenergized. This energization logic results in relatively constant acceleration and deceleration of the shirttle IO under varying load conditions, and the time delay logic compensates for the reduction in thrust M required after the shirttle 10 reaches the desired speed. do.

As shown in FIG. 3, the programmable controller 20
i to the primary, secondary and final energization stages, IMJffΔ
, B, and C. Ring counter 56 is indexed by one count on each cycle of return-to-advance movement of shuttlecock IO in response to no-load or human input from forward position limit switch 24.

It will be apparent to those skilled in the art that the disclosed embodiments of the invention can be adapted to control various numbers of linear motors and other operating requirements.

[Brief explanation of the drawing]

FIG. 1 is a schematic representation of a control device according to the invention for reciprocating a plurality of linear motor stators for reciprocating a shuttle for advancing an article carrier through successive work stations; FIG. 2 is a distance measuring circuit of the control device of FIG. 1; and a block diagram showing the components of the speed measurement circuit, FIG.
3B is an extension of FIG. 3A; FIG. 4A is a representative velocity/time curve for the forward motion of the linear motor-driven shuttlecock of FIG. 1; Figure 4B shows the first distance/time curve for the return movement of the shuttlecock in Figure 1, and the fifth
The figure is a diagram showing another form of speed reference circuit. 20, programmable controller means, 32
,, distance measuring means, 34. ,,encoder means,
38. ,, comparison means, 40. ,,speed reference means, 4
6. ,,output means, 48-. binary counter. VELOCITY

Claims (1)

Claims: 1. A shuttle (10) for advancing a plurality of article carriers (12) through successive work stations, including a plurality of electrically energizable stators (18) with forward and backward movement; In the shuttle, the shuttle includes means (30, 32) for reciprocating the shuttle during forward and backward movement of the shuttle, and control means (30, 32) for adjusting biasing of the stator in response to the speed and position of the shuttle (10) during forward and backward movement of the shuttle. The means comprises encoder means (34) for generating pulsed output voltages in response to movement of said shuttle (10), each encoder voltage pulse having a period proportional to the speed of the shuttle carriage, and further indicative of a desired speed of the shuttle. voltage reference means for generating in response to each encoder voltage pulse a reference voltage pulse having a duration proportional to
40), and comprising comparison means (38) for comparing the period of each encoder voltage pulse with the duration of each reference voltage pulse, wherein the duration of the reference voltage pulse is less than and greater than the period of the encoder voltage pulse. said comparison means (
output means (46) connected to a distance signal (D1 ) to generate the means (
48) for maintaining said shuttle at said desired speed and for decelerating said shuttle in response to said distance signal (D1). Shuttle, characterized in that it comprises programmable controller means (20) responsive to a progressive speed signal (V1) for progressively energizing the number of said stators (18) necessary to decelerate to said desired speed. 2. means (26, 28) for determining the number of article carriers (12) to be advanced by said shuttle (10);
), the programmable controller means (20
) is responsive to a signal representative of the determined number of article carriers to thereby limit the number of actuated pre-stators. 3. The speed reference means (40) is connected to the shuttle (10).
) having a duration proportional to the desired creep rate of
A reference voltage pulse is generated in response to each encoder voltage pulse and is connected to said comparison means (38) and said output means (46).
) respectively define the period of each encoder voltage pulse as the second
Generating energizing and deenergizing creep velocity signals (V2) in comparison with a reference voltage pulse, said programmable controller means (20) responsive to said distance signal (D1) to cause said shuttle ( 10) in order to maintain the creep velocity signal (V2) at the creep velocity.
The shuttle control means according to claim 1 or 2, characterized in that the shuttle control means is responsive to. 4. Sensing means (2) for supplying a signal representing the forward position of the shuttle (10) and a signal representing the return position of the shuttle to the programmable controller means (20);
4, 22), said programmable controller means (20) energizes said stator (18) to activate said shuttle (10) in response to said forward position and said return position during return and forward movement, respectively. 4. The shuttle control means according to claim 3, wherein the shuttle control means is driven. 5. said speed reference means (40) generate in response to each encoder voltage pulse a third reference voltage pulse having a duration proportional to the desired return speed (V3) of said means (10); 38) and the output means (46)
compares the period of each encoder voltage pulse with the third reference voltage pulse to generate energization and deenergization speed signals (
V3), said programmable controller means (20) accelerating said shuttle (10) to said desired return speed (V3) in response to said forward position signal (24) and said return speed signal (V3). 5. Shuttle control means according to claim 4, characterized in that the required number of stators (18) are energized gradually. 6. The distance measuring means (32) generates a second distance signal (D2) in response to a comparison of the count value of the encoder voltage pulses with a second reference number representative of a desired distance that the shuttle will travel upon return. Shuttle control means according to claim 5, characterized in that said programmable controller means (20) is responsive to said second distance signal (D2) to decelerate said shuttle during its return movement. 7. Shuttle control means according to claim 6, characterized in that said programmable controller means (20) controls the gradual energization of said stator (18) at desired time intervals. 8. said programmable controller means (20) comprising ring counter means (56) for rotating the sequence in which said stator (18) is energized in successive cycles of forward and return movement of said shuttle (10); The shuttle control means according to claim 7.