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    • 专利摘要:
    18 m A computer numerical control system (2), comprising a control unit (4) configured togenerate control signals (6) to be applied to two rotation generating units (8, 10), a firstrotation generating unit (8) and a second rotation generating unit (10), the first rotation generating unit (8) is configured to generate a rotation of a first axle (12)along a first longitudinal axis A. The second rotation generating unit (10) is conf1gured togenerate a rotation of a second axle (14) along a second longitudinal axis B. The axes Aand B are parallel and offset. A first object (16) is connected to said first axle (12),Wherein said first object (16) has a two-dimensional extension in a plane perpendicular tosaid first axis A, and a second object (18) is connected to said second axle (14), Whereinsaid second object (18) has a tWo-dimensional extension in a plane perpendicular to saidsecond axis B. The control unit (4) is conf1gured to deterrnine control parameters byapplying predef1ned control algorithms and to apply said control signals (6) to controlrotations of said first and second axles (12, 14) such that a desired target configuration(20) of a target item (22) attached to said first object (16) is achieved by an actuator (24)attached to said second object (18). (Figure 1)
    公开号:SE1451274A1
    申请号:SE1451274
    申请日:2014-10-24
    公开日:2016-04-25
    发明作者:Bruno Bosco
    申请人:Bruno Bosco；
    IPC主号:
    专利说明:

    Computer numerical control device Field of the inventionThe present invention relates to a device according to the preamble of the independent claim.
    In the text the following abbreviations are used:PCB Printed circuit board CAD Computer Aided Design CAM Computer Aided Manufacturing NC Numerical Control CNC Computer Numerical Control SMD Surface-mount devices CAE Computer Aided Engineering ECAD Electronic Computer Aided DesignEDA Electronic design automation FAB PCB Fabricator Background of the invention Traditional equipment for producing circuit boards on a small scale has been eitherexpensive, labour heavy and/or bad for the environment. The tWo main methods forproducing prototype PCB:s are chemical etching and CNC routing. Chemical etchingrequires quite small economical resources but requires the handling of hazardouschemicals, Well ventilated areas and skill. This makes chemical etching unf1t for manyenvironments and circumstances. The other main method for prototyping circuit boards isto use a computer controlled milling to engrave the surface of a copper laminate. Thisprocess is easy to use, does not require any dangerous chemicals and can produce veryreliable results. The draWback of the milling technique has been the high initial investmentneeded to purchase the machine itself and maintenance. Due to the prices today (typically7000-15000 USD), it is often not economically viable for a company to buy a CNC mill specialized in only producing PCB:s.
    This application describes the development and evaluation of a low cost CNC platformwhich can make PCB prototyping ability available at a price point where it is accessiblefor smaller companies, universities and amateurs alike.
    The platform has also been made compatible with some common ECAD/EDA softwaretools, making it easy to use.
    The demand for creating fast and reliable prototype circuit boards has grown significantlyduring the last few years. Electrical components have been rapidly shrinking in size andwe are now seeing a development where SMDs (Surface Mounted Devices) are cheaper,smaller and more efficient than their through-hole counterparts. SMD:s have thedisadvantage of being harder to prototype and test than through-hole components sincethey cannot easily be mounted on solder-less boards and other commonly used prototypingequipment. In fact even simple measurements can sometimes be hard to perform on someSMDs without creating a prototype circuit board for the component.
    Therefore the need for developers to produce their own PCBs (Printed circuit boards) ishighly demanded. Traditional designs of CNC systems norrnally use linear actuation to move in each axis, e.g. three linear actuators are used to move a tool in space.
    Related technique is described in the following documents: US-7283889 relates to a numerical control device and method. The method uses anumerical control device for a machine having at least three axes of linear motion, a firstaxis of rotation for rotating a tool head, and a second axis of rotation for rotating the toolhead, the second axis of rotation being arranged above the first axis of rotation.US-20l2/0203374 relates to a numerical controller for making a positioning completioncheck. The numerical controller calculates the distance (rotation radius) between therotation centre axis and a control target point using the machine conditions of a machinetool having a rotary axis and the coordinate values of the respective axes of the machinetool.
    The object of the present invention is to reduce the mechanical complexity and cost ofCNC systems, and thereby to achieve an improved CNC system, herein denoted “TheRotary Design”. The viability of the Rotary design as a low cost PCB router is evaluated in detail in this application. 3 One further object of the present invention is to develop, implement and evaluate a first prototype of the machine and to achieve a low cost, PCB milling platform.
    Summarv of the invention The above-mentioned objects are achieved by the present invention according to theindependent claim.
    Preferred embodiments are set forth in the dependent claims.
    The Rotary design is intended to keep the mechanical complexity of the machine to aminimum. The decrease in complexity will enable a lower production price and lessnecessary maintenance than the machines that are currently on the market.
    The use of rotational motion can reduce the number of moving parts and mechanicalcomplexity of the system.
    The system comprises of a two rotating axes and one (optional) linear axis. The tworotating axes are controlled using stepper motors, servo motors, brushless DC motors orother suitable actuators to tum a tool around one of the axis and a build table around theother axis. By controlling these actuators a tool, attached with an offset from one of therotating axes, can be moved in any continuous 2d path within the build plate.
    By employing a third actuator a linear axis can be used to control either the position (Z-coordinate) of the build table or the Z-position for the tool. This enables the tool to movein 3d space.
    The figures show an implementation where two rotational axes and one linear axis hasbeen implemented. A spindle is attached to the top rotating axis, while the build plate(with a copper laminate attached to it in this case) is attached to the lower of the tworotating axes. A linear axis which controls the linear motion of the build plate is alsovisible.
    The arm at which the tool is attached is in this implementation set to be half the length ofthe radius and the build plate. This optimises the reach of the tool while minimizing theforces at the tip of the tool.
    A microcontroller is used to keep track of the current position, read in information of thedesired position and calculate how much each axis must rotate in order to reach the desired position. Figure 4 shows a flow chart over the process. 4 The system may be applied in relation to laser cutters, 3d printers, CNC mills, automateddrawing applications, and other CNC systems, where a tool or sensor device must bemoved automatically in space.
    The invention relates to a CNC system which uses two rotational axes and optionally onelinear axis to position a tool in 3D space, and in particular the invention relates to featuresfor performing navigation in the XY- Plane). In the XY plane the movement is controlledonly by using the rotational axes while the Z axis is controlled by a linear actuator.Dedicated software has been developed to control each axis in such a way that the tool canbe moved to any position through a specified path. The invention consists of both thephysical design of the system (the concept of using two rotational axes to navigate the XYplane) and the control system which makes it possible to move the tool to any point in theplane through any path using only the two rotational axes.
    The main physical components of the system are a rotating base plate (where for examplea substrate to be cut or milled can be placed), a rotating actuator arm (holding the tool) andan optional linear actuator controlling the Z position of the tool. Each of these componentsis controlled by a motor which in tum is controlled by an embedded platform. On theembedded platform software has been implemented to synchronize the movement of eachmotor in order to make it possible to move the tool in a desired path. The physicalstructure that supports these main components is embodied by a prototype. The prototypedemonstrates the function of navigating a tool in the XY plane by using two rotationalaxes.
    One object of the present invention is to achieve a low cost CNC-machine that is capableof reliably producing prototype circuit boards. In order to conduct the evaluation aprototype implementation of the rotary design will be implemented. The prototype shouldhave full functionality in the XY plane and should include an implementation ofmovement along the Z-axis. Some measurable goals have been set for the final product.The first prototype should be able to either confirm that these goals are reachable orprovide arguments as to why they are not. The stated goals for the final product are listedbelow: - Have a precision of the end mill position in the XY-plane of less than 0.l mm in anydirection - Be able to interpret and execute some standard G-code commands.
    - Have a material cost under 500 USD.- Be able to repeatedly produce circuit boards with footprints of a LQFP capsule with 0.5mm pitch.
    Short description of the appended drawings Figure 1 is a block diagram schematically illustrating the present invention.
    Figure 2 is a block diagram schematically illustrating one embodiment of the presentinvention.
    Figure 3 is a graph showing equations for calculating control parameters.
    Figure 4 is a flow diagram illustrating a procedure for realising the present invention.Figures 5 and 6 show schematic perspective views illustrating the computer numericalcontrol system according to the present invention.
    Figures 7 and 8 show schematic perspective views illustrating the computer numerical control system according to one embodiment of the present invention.
    Detailed description of preferred embodiments of the invention The present invention will now be described in detail with references to the appendedfigures.Throughout the figures the same or similar items will be designated the same reference signs.
    First with reference to the schematic block diagram shown in figure 1, the presentinvention relates to a computer numerical control system 2, comprising a control unit 4configured to generate control signals 6 to be applied to two rotation generating units 8,10; a first rotation generating unit 8 and a second rotation generating unit 10.
    The control unit is e.g. a computer provided with processing capability and including amemory. The control unit also includes all required circuitry to provide, to generate and toapply the control signals to extemal units, e. g. electrical cables.
    The first rotation generating unit 8 is configured to generate a rotation of a first axle 12along a first longitudinal axis A, and the second rotation generating unit 10 is configuredto generate a rotation of a second axle 14 along a second longitudinal axis B.
    As will be further discussed in the following the rotation unit may be e.g. a stepper motor.
    According to the invention the axes A and B are parallel and offset.
    A first object 16 is connected to the first axle 12, wherein the first object 16 has a two-dimensional extension in a plane perpendicular to the first axis A.
    A second object 18 is connected to the second axle 14, wherein the second object 18 has atwo-dimensional extension in a plane perpendicular to the second axis B. The control unit4 is configured to deterrnine control parameters by applying predefined control algorithmsand to apply the control signals 6 to control rotations of the first and second axles 12, 14such that a desired target configuration 20 of a target item 22 attached to the first object 16is achieved by an actuator 24 attached to the second object 18.
    Preferably, the control parameters provides for simultaneous rotation of the first andsecond axles 12, 14.
    The rotational units are naturally attached to a rigid structure which for sake of simplicitynot is included in the schematic illustrations in figures 1 and 2. Different examples of thisstructure are shown in figures 5-8.
    According to one embodiment the desired target configuration 20 is a two dimensionaltarget configuration, i.e. a configuration in the X-Y-plane defined by the plane of the first object.
    In one embodiment of the invention the first object is a circular board having a radius r,and arranged such that the first axle is attached to the centre of the circular board, and that the second axis B is arranged at a distance of approximately r/2 from the first axis A.
    The second object is preferably an elongated actuator arm 26 having a first end 28configured to be attached to the second axle 14 and a second end 30 configured for attachment of the actuator 24.
    In a preferred application, which will be discussed below, the CNC system is used forproducing printed circuit board (PCB) and the target item 22 is then a PCB and the actuator 24 is a printed circuit board (PCB) machining tool. 7 With references to figure 2 another embodiment of the computer numerical control systemaccording to the invention is illustrated. According to this embodiment the control systemis used for producing three-dimensional objects, i.e. the desired target configuration is athree dimensional target configuration.
    The system illustrated in the schematic block diagram of figure 2 is based upon the systemillustrated in figure l, but includes also a longitudinal movement arrangement 32configured to move the first and second objects in relation to each other along said axes A and B, in dependence of the control algorithms.
    As Will be further discussed below, and With references to figure 3, the control algorithmincludes goveming equations for each quadrant of a fiill rotation around axis A, definingthe position of the actuator on the first object including angle oi being the angle in relationto axis B and angle (9 being the angle in relation to axis A. The distance from the centre ofthe first object is only dependent on oi and the position around the edge of the circle With aradius of that distance is only govemed by (9, and that a unique equation for each halfplane is deterrnined. The algorithm fiarther comprises algorithm steps configured formoving the actuator the shortest distance between quadrants and for using the correct equation in each half plane.
    In order to evaluate the capability of the Rotary design a prototype has been developed.The operation of the prototype has been simulated in MatLab[8] in order to easier errorcheck, and visualize the goveming kinematic equations.
    The simulation also makes it easier to implement and test different softWare solutions suchas G-code interpretation and tool path optimization.
    The evaluation of the prototype parameters has been deterrnined empirically bymeasurement. Extrapolation of the result of the prototype to the capability of a finalproduct has been made With the help of literary studies, simulation and mathematical reasoning.
    This application Will focus primarily on the XY-plane fiinctionality of the Rotary design. 8 The reason for this is that the Z-axis functionality could be implemented using atraditional linear design which is already a widely adopted solution. However, one couldimagine that some custom solution could be developed for the final product.
    Software will be developed to the point at which an outline of a PCB trace can be drawnon a paper. From that point it is straightforward to provide an implementation for drillingand cutting ofe.g. a PCB.
    One object of the present invention is to implement the concept of the Rotary design°soperation in the XY-plane.
    The Rotary design is configured to reduce the mechanical complexity and cost of a CNCPCB routing machine. Traditional designs predominately uses linear motion in all axes.This results in the need for linear actuators which are expensive and sometimesmechanically complex. By using a rotating motion for positioning in the XY-plane theRotary design can reduce the cost and complexity of the CNC system. Figures 5 and 6demonstrate the design of a two-dimensional system.
    The Rotary design utilizes two axes of rotation in order to position a tool in the XY-planeinside the circular work envelope. The substrate 22 (copper laminate in this case) is placedand fastened on a rotating disk 16 (the base plate) in between the top and the bottom plateas depicted in figure 5. The disk is attached to the shaft of the planetary gear of the bottomstepper motor. A cutting tool is then fastened on the actuator arm, which in tum is fastenedon the motor shaft of the top planetary gear. The disk and actuator arm can now be rotatedin any 2D pattem by individually controlling the motion of each rotating axis. The controlmethod and kinematics behind it are covered in following sections of the description. Byplacing the actuator arm at half the radius from the centre of the base plate the forces at thetip of the arm are held at a minimum while maximizing the work area. It also optimizesthe arm in terms of resolution since a longer arm means more movement at the tip per step of the motors.
    Figure 5 shows a model of the system when applied in a PCB (Printing Circuit Board)milling situation. A copper laminate 22 is placed on the base plate 16 while a spindle motor 18 is positioned at the tip of the actuator arm.
    The actuator arrn and base plate can now be controlled to move the cutting tool (attachedto the spindle motor) in a specified path. A pattern can thereby be cut out in the copperlaminate to create a circuit board.
    The prototype uses a pen as a tool to trace the motion on a piece of paper (see figure 6).
    One drawback of the Rotary design is that it does not scale well with an increasing workenvelope since the forces on the end of the actuator arm grows with the length of the arm.Traditional linear designs stem from big, heavy duty industry applications and in thatcontext the Rotary design would probably not perform well because of the increasingforces. This is possibly one of the reasons why it has not been developed before and whyother similar designs of a CNC machine not have been found.
    For the relatively small work envelopes that are used in desktop and table-top machineshowever, the Rotary design offers many advantages over traditional designs. Some of theadvantages of the Rotary design are listed below: - Less maintenance due to reduced mechanical complexity - Lower cost due to fewer parts and fewer production steps.
    - Greater mobility since the construction can be disassembled and reassembled in an easyway.
    - Smaller footprint due to fewer mechanical parts.
    Derivation of kinematics In order to create a simulation of and to control the Rotary Design the inverse kinematicsof the end mill position has been derived. Figure 3 shows a schematic configuration of thedesign, where the goveming equations for (9 are inserted in each quadrant.
    The dot, designated “EndMillPos” (see arrow in figure 3), indicates the location of the tipof the actuator arm and its position of the end mill is governed only by the two angles otand (9. The outer circle shows the work area and the smaller circle shows the reach of theactuator arm. Ybase and Xbase define the coordinate system of the base plate while itrotates around origo. Yarrn and Xarrn define the coordinate system of the actuator armwhile it rotates around the point where the arm is fastened (in this case at half a radiusdistance from origo). The distance from the centre of the base plate is only dependent on ot and the position around the edge of the circle with a radius of that distance is only lO govemed by (9. Since the kinematic equations have more than one solution a uniqueequation for each half plane has been derived. Logic has then been implemented insoftware to ensure that the control system moves in the shortest distance betweenquadrants and that the correct equation is used in each half plane. The procedure is 5 illustrated in the detailed flow chart in figure 4.
    Equation l-4 (see below) shows the derivation of the inverse kinematics for the upper halfplane of the depicted system. The equations for the lower half plane have beenanalogously derived. l0 The distance from the origin, N, (centre of the base plate) is only dependent on the angle ot. This relationship can be expressed as in equation l below. x W - af* w s. '* X) N "- ~.. I* ä» ¿3, {* Ö \__ *i 5:. _ <§.-*“ °-f~ Ma» =.>;-°-'_ ß <~.'-~; ; -\. .3 .V _g§f *'¿*.f"~"":->š¿§ *i *Fi.-- f. :;.-{.P<.- \_ ,\_ a» I:.s t... l5 Where N is the distance from the point (xp; yp) of the origin to the base plate, and ot is theangle of the actuator arm. Rarrn is the length of the actuator arm.
    Using the solution for ot, a solution to (9 can now be derived.
    .W ____ __ 'v _. _... -' ft _. *___ _. ÅÄ gšj... «~- ~~~~ flfgšrë -.---~--.<.ïs_.>.*:<¥ ~~~~ ~~ s<_ï=__.f:«: t .As3.. hu :Rv . ä: 4; _ _:.i fffšï _. . _ Ik +_§ - ~' åf-ä:t“;-*fï:t šf šïà-frï §.=ïv§š,§,š=ï.§:r m Éšàwt: fri ;â.=*§~f..=ïs«f;:t. a. ll The system will be powered by 1.8 degrees/ step planetary geared stepper motors.The motors are driven by drivers which are capable of micro stepping down to 1/16 steps(stepRatio = 16). Equations 5-7 are used to calculate the theoretical resolution of the systern across the work envelope. f» ~--~ 'x š -'"-*< _. .. gå .. . *in ~§ .fl ' -. - *RÅ . ajg. _. ._ 'ryms ' . . _ fša-s: ._ xÖ. .~à':ï}*.1-*á$_._“ ^É},<“~:ï'<ï.-~:'.§.=.'ät-å 'ä-»ífïš- -'-'-'-'-' """""" "iii" ä' ~..~~.*._-f}*.>§'":s_2.s :flsfiß årà-:xirš'šåï,šn.i_s»f..êiß .t _ ä. . t .
    Inserting the maximum step ratio of 16, the target resolution of 0.1mm and the maximum distance from the centre (e. g. 100mm) we can solve for the minimum gear ratio needed. <3 -. .--~ -. IM» :s ësàášflå šsf~r> “få .t _ “Ü ' ' 'f"åta;.wf.>àfss.äæ.¿ “- :_.~ i *JL 503.35 . MJ.- å: .då <1- å» .à-U: <- .f-r »Ft *w ~ ~'1 *X2 cin va f*- .ïf f*- -^ NM-Qà <.<-.,<_.:§». au” ;.-.{_:.< 1:. 2.3.: u _. _.
    The rotary design requires two rotating motions to navigate the XY-Plane. In order tocomply with the stated accuracy demands the base plate of the machine must becontrollable to a level of at least 6284 steps per revolution (see Equation 5). The Actuatorarm only requires half the number of steps per revolution to achieve the same accuracy butin order to keep complexity and costs down the same motors and transmissions has beenapplied to both axes.
    After exploring several options (discussed in detail in this section), l.8degrees=stepstepper motors with a 5+(2/1 1) planetary gear was selected. This design reduced the needfor a secondary gearing stage such as a worrn gear or belt drive which would inducefurther mechanical complexity. Naturally, solutions including worrn gears and/or beltdrives may also be used and are within the scope of the present invention which is definedby the claims.
    Stepper motors with integrated planetary gearboxes are readily available in standard NEMA sizes and falls within the stated budget goals of the machine. The base plate and 12 actuator arm are driven directly from the planetary gear shafts. For increased radialstability, ball bearings has been added to each shaft and mounted on the base and top plates of the machine.
    The stepper motors are controlled by Big Easy® drivers. The drivers allow for switchingbetween full, half (1/2), 1A, 1/ 8, and 1/16 steps. In combination with the planetary gearsthis results in a maximum resolution of 165 82steps per revolution or 0:03789mm=step ofthe base plate at the edge of the base plate (see Equation 6). Since the actuator ispositioned at half the base plate radius it will move with a resolution of 0.01895mm=stepusing the same set up. Each motor (including the planetary gear) is capable of producingconstant torque of up to 2.0Nm. Meanwhile a typical force while milling PCB boards isabout 2.8N according to accurate CNC. This would make the torques on the edge of thebase plate about 0.1 * 2.8 = 0.28Nm, thereby giving some head room for the intended useof the motors. This is important since losses in torque might occur during micro-stepping and transmission.
    At any point inside the work envelope one step of either the arm or the base plate can beapproximated as a straight line. This allows for a simple estimate of the theoreticalresolution of the machine. Using this approximation we get the result that the system has atheoretical ability to position the actuator inside a rectangle of 0.03789*0.01895 =0.0007mm2 or less at any point within the work envelope. The actual resolution howeverwill be constrained by other physical factors such as vibrations and flexing as well as calibration and inaccuracies in gearing, calculations and a number of other factors.
    The techniques that are used to control CNC-systems can be divided up into two distinctapproaches. Closed-loop control (Servo drive) and open-loop (Stepper drive) control.Both approaches have their advantages and disadvantages, which are discussed in the following two sections.
    In an open-loop system there is no feedback from the system during operation. This makesit impossible to recover from un-modelled variances imposed on the system from the process. It is therefore necessary that all actuators are able to execute the commands from 13 the controller in order for the system to work properly. Open-loop systems are thereforeonly suitable for applications where the process is repeatable and reliable and has a verylow variance in its operation. In essence the model of the system needs to be near perfectin order for the system to perform as expected. However, if the model is accurately set upthe open-loop approach can greatly reduce the complexity and cost of the system sinceless hardware (sensors and feedback circuitry) is required. Stepper motors are common inOpen-loop systems and perforrns well under the right circumstances and seems to be the preferred choice for most open-loop CNC systems.
    Closed-loop system allows for precise control of angular position, Velocity andacceleration. It consists of a suitable actuator that has a feedback-sensor which indicatesthe state of the system back to the controller. The controller needs to be relativelysophisticated and usually needs some tuning to work properly. A common technique forthis is to implement a PID controller. For closed-loop CNC systems servo motors arecommonly used. Servo motors have an intemal feedback system which makes it possibleto adjust for unintended deviations from the desired position of the rotor. This ability makes the system less susceptible for un-modelled aspects of the process.
    Deciding between open-loop (stepper motor), closed-loop (servo motor) or some sort ofcombination of both has been a challenge. Design factors such as cost, complexity,dynamic response, torque, speed, acceleration and controllability need to be considered inorder to make a wise choice regarding the control loop an control strategy.
    There are usually some key design criteria like cost, positional accuracy requirements, torque requirements and availability, which all need to be concemed wisely.
    Servo motors generally perform better regarding speed, power and the ability tocompensate for errors. However, high cutting/engraving speed is not a crucial feature forthis system at hand. Since stepper motors will be able to move the engraving tool or penfast enough in the XY-plane (use different stepping techniques like full-step, half-step andmicro-stepping). The decision to use an open-loop control approach with stepper motors has been decided for the following reasons. 14 - The speeds involved in the routing process is Well Within What stepper motors can handleand examples can be found in existing CNC systems.
    - The torque requirements of the system are also Within the specif1cations of manycommon stepper motors.
    - The physical size of the motor is a standard, (N ema Standard).
    - Therefore is it possible to purchase them from any supplier and it Will still fit Well Withthe machine. The frame-size Will be the same it Will only be some differences in heightdepending on how much torque the user wants.
    - The theoretical accuracy, Within the limits of the stated goals, can be achieved usingstepper motors, by using gearing and drivers capable of micro stepping.
    - Servo motors are more expensive than stepper motors, and to minimize cost and achievethe 500 USD price. A stepper motor is a more suitable choice With regard to price.
    - If needed the stepper motors could be equipped With encoders and/or rotary potentiometers to provide relative/absolute positional feedback.
    According to one embodiment of the present invention instead a closed loop system using a servo drive system is applied in order to implement the present invention.
    There are a lot of different stepper motors on the market today. The basic theory aboutstepper motors is therefore necessary, in order to be able to make a Wise choice regarding the specif1cations of the stepper motors and their performance.
    Stepper motors use pulses as input, and converts the pulses into mechanical motion Whichis proportional to the motors step angle. Stepper motors are based on the fact that a rotorhas a tendency to align itself to Where the magnetic field (stator flux) has its maximum,Which is the position Where the rotor has minimum reluctance. The shafts position isdirectly deterrnined by the number of poles in the stator Which the driver supplies currentthrough. Depending on the current applied, different torques can be achieved.
    A revolution is divided into a series of discrete states (steps) Where each step rotates theshaft a certain number of degrees. Standard (hybrid) stepping motors have 200 or 400"rotor teeth" also commonly called poles or coils. If a motor has 200 poles this means that it Will require 200 full steps in order to complete one revolution of the motor shaft. The angle travelled for each step Would then be 360°/200steps resulting in that l.8° equals onestep Which is referred to as the motors step angle.
    Stepper motors are commonly used in applications such as automation, robotics,machinery and common in digital control systems because of the discrete nature of theiroperation.
    Stepper motors are categorized in three main categories Which are based on tWo differenttechniques. Permanent magnet (PM) stepper motors, Variable reluctance (VR) steppermotors and hybrid stepper motors Which is a combination of PM and VR. The categorythat is eventually chosen is naturally dependent on the specific demands required in specific applications.
    Figures 7 and 8 show schematic perspective views illustrating a three-dimensional versionof the computer numerical control system, according to the present invention. Thelongitudinal movement arrangement 32 is configured to move the first and second objects in relation to each other along said axes A and B, in dependence of the control algorithms.
    The present invention is not limited to the above-described preferred embodiments.Various altematives, modifications and equivalents may be used. Therefore, the aboveembodiments should not be taken as limiting the scope of the invention, Which is defined by the appending claims.
    权利要求:
    Claims (10)
    [1] 1. A computer numerical control system (2), comprising a control unit (4)configured to generate control signals (6) to be applied to two rotation generating units (8,10), a first rotation generating unit (8) and a second rotation generating unit (10), the first rotation generating unit (8) is configured to generate a rotation of a first axle (12)along a first longitudinal axis A, the second rotation generating unit (10) is configured to generate a rotation of a secondaxle (14) along a second longitudinal axis B, c h a r a c t e r i z e d i n that said axes A and B are parallel and offset, and that a first object (16) is connected to said first axle (12), Wherein said first object (16)has a two-dimensional extension in a plane perpendicular to said first axis A, and a second object (18) is connected to said second axle (14), Wherein said second object (18)has a two-dimensional extension in a plane perpendicular to said second axis B, Wherein said control unit (4) is configured to deterrnine control parameters by applyingpredefined control algorithms and to apply said control signals (6) to control rotations ofsaid first and second axles (12, 14) such that a desired target configuration (20) of a targetitem (22) attached to said first object (16) is achieved by an actuator (24) attached to saidsecond object (18).
    [2] 2. A computer numerical control system according to claim 1, Wherein saidcontrol parameters provides for simultaneous rotation of said first and second axles (12, 14).
    [3] 3. A computer numerical control system according to claim 1 or 2, Wherein said desired target configuration (20) is a two dimensional target configuration.
    [4] 4. A computer numerical control system according to any of claims 1-3,Wherein said first object is a circular board having a radius r, and arranged such that saidfirst axle is attached to the centre of the circular board, Wherein said second axis B is arranged at a distance of approximately r/ 2 from said first axis A.
    [5] 5. A computer numerical control system according to any of claims 1-4, 17 Wherein said second object is an elongated actuator arrn (26) having a first end (28)configured to be attached to said second axle (14) and a second end (30) configured for attachment of said actuator (24).
    [6] 6. A computer numerical control system according to any of claims 1-5,Wherein said actuator (24) is a printed circuit board (PCB) machining tool, e. g. a laser cutting tool.
    [7] 7. A computer numerical control system according to any of claims 1-6, Wherein said first and second rotation generating units are stepper motors.
    [8] 8. A computer numerical control system according to any of claims 1-7,Wherein said system comprises a longitudinal movement arrangement (32) conf1gured tomove said first and second objects in relation to each other along said axes A and B, in dependence of said control algorithms.
    [9] 9. A computer numerical control system according to claim 8, Wherein said desired target configuration is a three dimensional target configuration.
    [10] 10. A computer numerical control system according to any of claims 1-9,Wherein said control algorithm includes governing equations for each quadrant of a fiJllrotation around axis A, def1ning the position of the actuator on the first object includingangle ot being the angle in relation to axis B and angle (9 being the angle in relation to axisA, Wherein the distance from the centre of the first object is only dependent on ot and theposition around the edge of the circle With a radius of that distance is only govemed by (9,and that a unique equation for each half plane is deterrnined, the algorithm furthercomprises algorithm steps configured for moving the actuator the shortest distance between quadrants and for using the correct equation in each half plane.
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    SE539286C2|2017-06-20|
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