Use module of computation of PLC high speed to undertake the axis locates

1 foreword is in numerical control system, when working like cutting machine tool, often undertake controlling to the feed speed of cutting tool and mobile position, many PLC configured module of axial fixed position in the product, with the movement that will control a pace technically to enter electric machinery or servo electric machinery, to certain PLC, should control module into electric machinery without the pace or when PLC itself contains high speed computation to input a dot, also can realize axial fixed position with method of high speed computation, pilot of axial location system basically is opposite seem the place, usually, the roll of electric machinery is accused with transmission machinery translate into the sharp movement of the object. 2 axes locate the principle often locates the command asks shift of the spare parts on the axis arrives when another position, module is calculated first an academic time rate plan. Control an axis with plan of this time rate next, the made position that obtains a provision finally. Typical time rate plan is an echelon, that is to say, the axis moves with the acceleration of acceleration A divide evenly of user set first, till achieve V of user set rate, next the time with proper uniform motion, again the acceleration A divide evenly with user set retarded motion, turn into till speed 0. Speed arrives 0 when, the P is worth Δ that the space just in time with mobile axis is command regulation. According to time rate plan, can calculate piece corresponding location drawing of a time. Rotate to be not being taken the open loop pace of coder enters control module, speed commands the value that pulse pursues with time speed is outputted, when Δ P after pulse is outputted entirely, stop to output. In the closed-loop control way that with rotating coder makes the position feedback, each hour, the position on time location drawing is fiducial value, rotate coder feedbacks those who come back is real value, this both difference is position error namely. The product that uses position error and positional annulus gain commands output as speed. The position error that method of this kind of control can assure to locate finally is adjacent 0. Because this is,one kind is controlled without deviation, want to have an error only, can have the rate that eliminates this error, turn into to the error all the time 0. When be being controlled with this kind of method, position error is bigger, the rotate speed of electric machinery is higher. When position error is not changed, electric machinery with divide evenly fast roll. When position error decrescent, electric machinery with respect to decelerate. Want electric machinery to suspend campaign, position error must is 0. In process of fixed position campaign, the oldest rate of electric machinery won't exceed academic career maximum. Because be in athletic process in the begining, position error from 0 greaten slowly, speed commands the value also greatens slowly, electric machinery rotate speed rises. Level is quickened in theory, speed commands the cost always is less than academic career. So, accumulate ceaselessly as position error, speed commands the value greatens ceaselessly, electric machinery also is quickened gradually. In divide evenly fast phase, if fast drag out a miserable existence makes still be less than academic career, so position error still can increase, speed commands the value also can increase. But increscent limit is speed order value is equal to academic career. When both and equal when, position error greatens no longer, electric machinery runs with academic career. In decelerate phase, speed jussive decelerate is slower than academic career, then the position by accident taper, corresponding ground speed commands a value also decrescent. It is when academic career 0 when, the position error that accumulates previously has not decreased to 0, so still speed commands output. This output is to position error 0 when just can end. The area under two speed-distance curve is displacement quantity of motion namely, both it is equal. The relation of these two speed can use the following formula to express: In F of 〕 of VR(t)dt of VT(t)dt- ∫ of VR(t)= 〔 ∫ or type: VR(t) , effective rate; VT(t) , academic career; F, positional annulus gain, it is the reciprocal value of time. A solution of afore-mentioned relation be: In VR(t)=v0e-ft type, v0 is some constant. When speed VT(t) is constant, solve especially for: In VR(t)=v0e-ft+vT(t) type if VT(t) is constant, when T enough big when, VR(t)=vT(t) , namely effective rate is equal to academic career. As long as E-ft is enough small, effective rate is right of academic career follow the error is equal to 0. The module of high speed computation of PLC of computation of 3 high speed is readable take average input drop to read the high speed pulse that does not take, right have count, use pulse outputs motor of electric machinery of function and pulse alignment instruction servo to cooperate, can make a rod tabulator. The module of high speed computation of SZ-4 PLC uses Z-CTIF, adding in decreasing tally, what can undertake 24 set are worth area amounting to is multistage set, when having count, computation value and set value are compared, below the condition that allows to interrupt, when set value and computation value are consistent, interrupt current processing to turn go carrying out suspend a program, interrupt a program to be carried out, return place be discontinuoused to continue to be carried out downward. When roll of drive guide screw undertakes the axis locates, can 2 kinds of methods undertake controlling: It is to undertake be accelerationed equably, to uniform motion, arrive again the process of decelerate, if graph 3(b) place is shown, in the begining the rate movements with 200pps, come quickly inside 1 second of time 2kpps, with 2kpps constant rate movements, slowdown has when shortly will reach position position, slowdown time also is 1 second, inside 1 second speed is decreased for 0, fixed position movement ends, arrive appoint the position. Another kind of method is to undertake multistage the kind that imposes decelerate to approach, if graph 3(a) place is shown, fixed position moves quickly with 200pps speed in the begining 100 pulse distance, move quickly with the speed of 400pps again 200 pulse distance, move quickly with the speed of 600pps again 300 pulse distance, steady movement phase moves with the speed of 800pps 1800 pulse distance, next decelerate moves, move with the speed decelerate of 600pps first 300 pulse distance. Move with the speed decelerate of 400pps again 200 pulse distance, move with the speed decelerate of 200pps again 100 pulse distance, finally fast turn into 0, end fixed position action, moved in all the distance of 3000 pulse. Axis of 4 application example locates the system chooses PLC of SZ-4 module type, the PLC of this model is to belong to exceed diminutive but program controller, use more convenient, the system chooses Z-CTIF of module of high speed computation together, inputted module Z-8ND1 at 8 o'clock together, outputted module Z-8TD1 at 8 o'clock together. Output end and frequency conversion motor connect, by the roll of motor drive guide screw, the rotational frequency of guide screw by rotate coder detects, rotate the module of sends PLC as a result high speed computation of coder, when specific echelon graph weaves, with multistage add decelerate pattern processing to go to the lavatory quite, multistage set value is put in register, when guide screw roll achieves set pulse to count, motor gearshift runs, when starting, quicken first, turn smoothly next, last slowdown comes position position. The instruction of gearshift part is put in suspending a program, every time when computation value and set value are consistent, special function register turns into ON, carry out interrupt an instruction. The system is multistage set value register begins to be in for R3630, go to input of value of 4 archives rate inside R3630-R3633. The input outputs the allocation of module: I10: I11 of starting switch 　 : Stop switch 　 Q10: Frequency conversion speed Q11 of 1 　 　 : Frequency conversion speed Q12 of 2 　 　 : Frequency conversion speed Q13 of 3 　 　 : Frequency conversion speed Q14 of 4 　 　 : Frequency conversion starts (ON)/ apply the brake (the function of axial fixed position that 5 conclusion of 　 of OFF) 　 　 realize with module of high speed computation can be used generally in automation equipment, if numerical control lathe or other need decide positional circumstance, more accurate to the control of the journey. Complex to fixed position of course case, echelon picture authorized strength has a place a little complex, had better use appropriative pace to control module or servo electric machinery to control module into electric machinery at this moment. But to the PLC like SH series, their itself is contained at 2 o'clock function of high speed computation, and because be integral type PLC, worse patulous situation controls module into electric machinery, use afore-mentioned methods to have very great application value and higher performance/price ratio. CNC Milling