毕业设计我帮你

法兰盘钻孔组合机床设计
摘要
为控制一种机械工具或类似物的位置数字控制手段通过辅助电动机来被描述。位置命令信号与表示辅助电动机位置的信号比较, 并且总值错误信号用来增加速度指令信号去控制操作马达的速度。每当错误信号高度超出一个被预先决定的水平时后续信号被产生, 并且后者增加来一个与系统结合的数字式位置信号。一个恒定的由前述继续采取的行动信号引起的数字信号来增加前述错误信号代替前述速度信号。
发明者 Pamela, Pinero; Laura, Lucia no;
分类
类318: 电: 驱动力系统
子类604: 模式比较
子类618: 车头表反馈 
描述 
发明的背景 
在机械工具或其它数字上受控用具里当前发明与一个为控制一个运动机件的位置和速度的系统相联系。在了解的系统运动机件里, 该位置上的沿一个或通过一台分开的辅助电动机几个轴中的每个, 以数字形式由程序单元提供的控制在一系列的连续位置和速度次序之下沿一个被预先决定的连续的道路运动。由一台对应的数字式对模式交换器各位置次序被转换成一个模拟信号和然后对位置探测器适应导致一个模式错误信号来提供如同一个命令信号相等与在运动机件的当前位置和由并且控制辅助电动机的速度的位置次序代表的位置之间的区别。
在这种了解的通常将譬如有一个恒定的在从位置探测器以运动机件的恒定的速度的产品的错误的系统里执行的伺服机械沿转移的轴运动。这型例子就是在我们的美国pat.第3,515,962 和3,356,994 和美国pat. 装置设备575,802中描述的安置的伺服机械。首要的这些由程序磁带位置次序的专利描述程序单元与被记录的相关安置点有非常紧密地关联,磁带的读者和记数器一度充足为各自命令传输对开动的伺服机械的一个连续的定位系统构成。另一方面,这些专利次要的,  就是包含唯一命令与分离点相关并且由一个适应作为产品命令与包括在程序的二连续分离点之间的一个连续的安置的安排所有中间点相关的供应供养磁带读者程序磁带来被描述。
位置误差由无法超出有些为了用机器制造不能获得的不精确的价值的位置探测器导致和特别是当循环位置探测器被使用时, 至于不丢失在有名无实的由连续安置的命令表明的位置和在转移期间由运动机件连续地获得实际位置之间的该步骤。 如果我们描述作为在速度和错误之间的比率K, 那是V/.epsilon., 用速度V也许用mm/sec 和错误.epsilon. 来表达。在毫米里, 在了解的伺服机械里对于K等级40是有价值的。因为.epsilon.无法超出被预先决定的价值, 可能控制辅助电动机是相当有限的, 即在此情况下.epsilon.不能超出0.5 毫米运动, 这是确切的。它的最大等级速度是20 mm/sec 。另一方面, 为了获得运动的更高的速度, 有一个更大的可利用的错误信号是必要的。用一个特别的方式由编程消除运动可能有不利的方面,那就是速度命令。速度命令, 而不是是行动在传输比率的一个特殊作用, 如此改变辅助电动机的速度, 是一个数值比例和它欲获得速度的绝对值。速度命令, 并且被转换成一个模拟信号, 来增加命令伺服机械的模拟错误信号。
发明的总结
因而, 根据发明的原则, 那里有一个更适合的具体化的描述的包括辅助电动机一可移动的沿一个连续的道路的部份的数字控制系统被提供, 以数字式形式程序单元适应供应一系列的连续位置和速度次序, 第一和第二个数字模拟转换器各自为这些次序成位置和速度指令模拟信号转换, 意味着在对位置命令信号和代表沿前述道路形成一个错误信号的可移动的部份的实际位置的反馈模拟信号之间的区别是敏感的, 和意味着在提供控制辅助电动机的速度的控制信号的错误信号上增加速度指令信号。 系统包括一台位置记数器并且更好的记录了速度, 然后继续记录了一个被预先的数字数量，此外每当错误信号的高度超出平实预先决定的数量,以补偿为手段的交换器在区别位置记数器的内容和计数后一次数之间的内容时,另一台交换器代替前一台速度记数器的内容。
图画简要的描述 
从发明的更适合的具体化的以下被给这种方式的例子的描述中发明的原则将更加清楚地被了解, 关于伴随的图画, 它显示一个数字控制系统的一张为机械工具的结构图。 
图画详细的描述
机械工具的程序单元包括被记录的一卷节目磁带1 位置和速度次序。这些次序, 由读者2 读, 被存放在对应的记数器Rp 里并且控制单元3 的Rv 直接地转移作为命令到开动在命令为沿一个连续的道路的案件有关控制运动完全地关闭的伺服机械, 或通过一处理器在控制单元在命令与沿一个连续的道路有关的案件的分离点相关被处理, 在命令的演算与在二连续分离点之间必需情况的中间点相关下。
寄存器Rp 的位置次序数字产品哺养一台数字式对模式交换器5, 模拟输出信号转移如同对错误探测器的命令或适应了错误信号epsilon的比较手段7.在机器的运动机件实际位置之间发信号在渠道11 的产物并且代表了由位置次序当前被提供给探测器的位置的区别是等同的。错误信号.epsilon.由放大器9 适当地放大, 适应命令在渠道11控制当前位置信号辅助电动机10 的速度。 
为了获得高速机器制造的速度,有一个可利用高错误信号.epsilon.会是必要的, 但这能导致用机器制造的不精确性。为了消除这个缺点, 那里被介绍入系统实现发明其它数字式对模式交换器6 由速度记数器哺养Rv 的数值和适应供应作为产品一个模拟信号比例与速度被编程为用机器制造。信号.epsilon.'从交换器6通过加法器8加来错误信号.epsilon., 和信号对应于.epsilon. 和.epsilon.' 的总和; 被结合对辅助电动机10 。这样, 高速度的达到以较大的精确度是可能的, 由于操作以小的位置误差信号.epsilon. 并且在任何情况下较少比信号对应于理论最大错误被允许。
当车速逐渐趋于等于零(减速阶段)这个位置误差介入指挥程控伺服,因而完善担保部分定位于移动程控点到达. 数码转六转换的速度模拟命令是比一般的简单结构转换为5 订单状况,因为它的行为简单线性转换. 在另一方面,转换器5可建成以供应三角尤其在模拟量数值地位与功能 它被供养, 在这个依赖结构所做的位置误差探测器7用于定位伺服. 可以观察到,在施工中被描述的控制系统关闭为止 在伺服回路是单独喂点输出信号转换5、6、 但没有行动的反馈伺服控制单元3到被形容。
如果理想的操作动作非常快,就是一个速度,例如10米的秩序/在预加工阶段, 校正了车速信号.epsilon.'就未免过大了最大误差信号.epsilon.，索取位置探测器. 事实上,假定循环运行状况进行了检测,以2毫米为步长, 理论上最大误差为0.5毫米, 而如果是在一个理想的操作速度=12米/分=200毫米/秒， 对于已经摆出K =40、 因此获得了速度信号.epsilon.'= V/Rv =200/40=5毫米; 即位置误差信号,可以在最高时相当于速度信号的10%。
为了快速动作,不同的运作方式被使用, 其中移动部分就应有地位被允许落后, 即使按最高金额大于允许理论误差以免失去一步. 这种运作模式,需要有配套手段顾及当前位置误差价值、在减速和到来阶段调整方案时起到达正常位置.
为此, 该系统体现了一种特殊的发明就是提供后续的包括控制单元3寄存器Ri，在误差13米的控制下一个持续数值Q被转换, 其中显示器输出误差探测器7 每当振幅定位误差产生的位置探测器127沿线超过某一 预定方式适合水平门槛在13米的误差. 因此,当输出是13米14被激活， 由此15门被使用、允许持续数值送到寄存器Ri, 这些供应量陆续总数. 此外,13米误差是改编,同时也是检测迹象,除了水平, 该错误.epsilon. ,因此,控制数量转移到数值Q相应具有正值或负值. 例如,每当位置误差.epsilon.正值超过+0.125毫米, 数值Q =+0.125毫米送到Ri、 而如果位置误差.epsilon.是负的，在-0.125毫米以下，数值Q=-0.125毫米将被送到Ri。
寄存器Rp、Ri的内容被应用于加法器4，它形成包含在RP的数字位置命令和在供养数字-模拟转换器5之前被引进的数值量之间不同点.. 另外后续寄存器的内容被送到转换器6代替速度寄存器Rv的内容. 这一点通过门16和门17以图表的形式表现出来，门16和门17分别控制后续寄存器Ri和速度寄存器Rv的输出，另外Rv由单元2的程序控制以便于它能使门16仅在快速时有效，而门17仅在相应慢时有效，而且最后的计算值进入速度寄存器Rv。另外当寄存器Ri的值是零时端口18的信号才能使门17有效，在19线上出现了由寄存器Rv发出的零速命令信号时，门16才有效。
这样，就存在一个位置误差.epsilon.。这个位置误差由位置探测器7测量，通常很小，而运动部分能落后于位置探测器测出的相应位置好几步。在要正确到达预定位置的最后阶段，后续寄存器允许当前寄存的测量位置误差被使用。
 
Numerical control system
Abstract 
Numerical control means for controlling the position of a machine tool or the like by means of a servomotor are described. A position command signal is compared to the signal indicative of the servomotor position, and the resultant error signal is added to a speed command signal to control the speed of operation of the motor. A follow-up signal is generated whenever the amplitude of the error signal exceeds a predetermined level, and the latter is added to a digital position signal coupled to the system. A constant digital signal generated by said follow up signal is added to said error signal instead of said speed signal. 
Inventors 
Pomella, Piero; Lauro, Luciano;
Classification 
Class 318: Electricity: motive power systems
Subclass 604: Analogue comparison
Subclass 618: Tachometer feedback
Description 
BACKGROUND OF THE INVENTION
The present invention relates to a system for controlling the position and speed of a moving part in machine tools or other numerically controlled apparatus. In known systems the moving part, position able along one or each of several axes by means of a separate servomotor, travels along a predetermined continuous path under the control of a series of successive position and speed orders supplied in numerical form by a program unit. Each position order is converted into an analogue signal by a corresponding digital-to-analogue converter and then supplied as a command signal to a position detector adapted to produce an analogue error signal equal to the difference between the current position of the moving part and the position represented by the position order and which controls the speed of the servomotor.
The servomechanisms which carry out the movement along the shifting axes in known systems of this type are normally such as to have a constant error in the output from the position detector with a constant speed of the moving part. Examples of this type are the positioning servomechanisms described in our U.S. Pat. Nos. 3,515,962 and 3,356,994 and U.S. Pat. Application No. 575,802. The first of these patents describes a continuous positioning system in which the program unit is constituted by a program tape on which position orders relating to very closely related positioning points are recorded, a tape reader and registers fed by the reader and adapted to store the successive orders for a time sufficient for the transmission of the respective command to the actuating servomechanism. The second of these patents, on the other hand, describes a continuous positioning arrangement in which the program tape contains only orders relating to discrete points and the tape reader feeds an interpolator adapted to supply as output the orders relating to all the intermediate points included between two successive discrete points of the program.
The position error produced by the position detector cannot exceed a certain value in order not to obtain inaccurate machining and, especially when cyclic position detectors are used, so as not to lose the step between nominal positions indicated by the successive positioning orders and actual positions successively attained by the moving part during the shifting thereof.
If we describe as K the ratio between speed and error, that is V/.epsilon., in which the speed V may be expressed in mm/sec and the error .epsilon. in mm, in known servomechanisms there will be values of the order of 40 for K. Since .epsilon. cannot exceed a predetermined value, it is clear that the maximum speed of movement with which it is possible to control the servomotor is rather limited, that is, in the case where .epsilon. must not exceed 0.5 mm, it is of the order of 20 mm/sec. On the other hand, in order to obtain higher speeds of movement, it would be necessary to have a larger error signal available.
This disadvantage can be obviated by programming the speed of movement, that is the speed order, in a special way. The speed order, instead of being a particular function which acts on transmission ratios, thus changing the speed of the servomotor, is a numerical value proportional to the absolute value of the speed it is desired to obtain. The speed order, having also been converted into an analogue signal, is added to the analogue error signal which commands the servomechanism.
SUMMARY OF THE INVENTION
Thus, according to the principles of the invention, there is provided herein a description of a preferred embodiment of a numerical control system comprising a servomotor for positioning a movable part along a continuous path, a program unit adapted to supply a series of successive position and speed orders in digital form, first and second digital to analogue converters for converting these orders into position and speed command analogue signals respectively, means responsive to the difference between the position command signal and a feedback analogue signal representing the actual position of the movable part along the said path to form an error signal, and means for adding the speed command signal to the error signal to provide a control signal which controls the speed of the servomotor.
Preferably the system comprises a position register and a speed register for storing the said orders, a follow-up register and means for transferring a predetermined numerical quantity thereto whenever the amplitude of the error signal exceeds predetermined level, means for feeding the first converter with the difference between the contents of the position register and the follow-up register, and means for applying the contents of the follow-up register, when these contents are other than zero, to the second converter in lieu of the contents of the speed register.
BRIEF DESCRIPTION OF THE DRAWING
The principles of the invention will be more clearly understood from the following description of a preferred embodiment of the invention given by way of example, with reference to the accompanying drawing, which shows a block diagram of a numerical control system for a machine tool.
DETAILED DESCRIPTION OF THE DRAWING
The program unit of the machine tool includes a program tape 1 on which position and speed orders are recorded. These orders, read by a reader 2, are stored in corresponding registers Rp and Rv of a control unit 3 to be directly transferred as commands to the actuating servomechanism in the case where orders sufficiently close for controlling a movement along a continuous path are concerned, or are processed by means of an interpolator in the control unit in the case where orders relating to discrete points along a continuous path are concerned, in which case the calculation of the orders relating to intermediate points between two successive discrete points is required.
The numerical output of the register Rp for the position orders feeds a digital-to-analogue converter 5, the analogue output signal of which is transferred as command to an error detector or comparison means 7 adapted to produce an error signal .epsilon. equal to the difference between the actual position of the moving part of the machine signaled over the channel 11 and the position represented by the position order currently supplied to the detector. The error signal .epsilon. suitably amplified by an amplifier 9, is adapted to command the speed of a servomotor 10 which controls the current position signal on the channel 11.
In order to obtain high machining speeds, it would be necessary to have a high error signal .epsilon. available, but this could cause inaccuracies of machining. To eliminate this drawback, there is introduced into the system embodying the invention another digital-to-analogue converter 6 fed by the numerical value of the speed register Rv and adapted to supply as output an analogue signal proportional to the speed programmed for the machining. The signal .epsilon.' from the converter 6 is added through an adder 8 to the error signal .epsilon., and a signal corresponding to the sum of .epsilon. And .epsilon.' is coupled to the servomotor 10. In this way, the attainment of high speeds with great precision is rendered possible, inasmuch as operation with a position error signal .epsilon. which is small and in any case less than the signal corresponding to the theoretical maximum error is permitted.
This position error intervenes to command the servomechanism when the programmed speed tends progressively towards zero (deceleration phase) and thus guarantees perfect positioning of the moving part at the programmed point of arrival.
The digital-to-analogue converter 6 for the speed orders is in general of simpler structure than the converter 5 for the position orders, inasmuch as it acts by simple linear conversion. The converter 5, on the other hand, may be constructed so as to supply at the analogue output particular trigonometrically functions of the numerical position with which it is fed, this being done in dependence upon the structure of the position error detector 7 used in the positioning servomechanism.
It can be observed that in the construction of the control system which has been described so far the closed loop of the servo system is fed at separate points by the output signals of the converters 5 and 6, but no feedback action of the servosystem into the control unit 3 has been described.
If it is desired to operate with very rapid movements that are at a speed, for example, of the order of 10 m/min, in the stages of presetting the machining, the correction given by the speed signal .epsilon.' would be too great with respect to the maximum error signal .epsilon. Obtainable from the position detector. In fact, assuming that operation is carried out with a cyclic position detector with a step of 2 mm, the theoretical maximum error is 0.5 mm, while if it is desired to operate at a speed of V = 12 m/min = 200 mm/sec, for K = 40 as already assumed hereinbefore, there is obtained a speed signal .epsilon.' = V/Rv = 200/40 = 5 mm; that is, the position error signal can be at a maximum equal to 10% of the speed signal.
For rapid movements, a different method of operation is therefore used, in which the moving part is permitted to lag behind with respect to the desired position, even by an amount greater than the maximum theoretical error permitted so as not to lose step. This mode of operation requires that there be auxiliary means which take account of the value of this current position error and allow a readjustment to the programmed nominal position in the phase of deceleration and arrival.
To this end, the system embodying the invention is provided with a special follow-up register Ri incorporated in the control unit 3 and to which a constant numerical quantity Q is transferred under the control of an error meter 13, which monitors the output of error detector 7, whenever the amplitude of the position error produced by the position detector 7 along the line 12 exceeds a given level predetermined by means of a suitable threshold in the error meter 13. Therefore, when the output 14 of the meter 13 is activated, the gate 15 is consequently enabled and permits the transfer of the constant quantity Q to the register Ri, which totals these successively supplied quantities. Furthermore, the error meter 13 is adapted, as well, to detect the sign, in addition to the level, of the error .epsilon. and, therefore, to control the transfer of the quantity Q to Ri correspondingly with a positive or negative sign. For example, whenever the position error .epsilon. is positive and exceeds + 0.125 mm, a quantity Q = + 0.125 mm is sent to Ri, while if the position error .epsilon. is negative and below -0.125 mm, the quantity Q = -0.125 mm will be sent to Ri.
The contents of the registers Rp and Ri are each applied to an adder 4, which forms a difference between the numerical position order contained in Rp and the numerical quantity introduced into Ri before feeding the digital-to-analogue converter 5.
The contents of the follow-up register are moreover sent to the converter 6 in place of the contents of the speed register Rv. This is shown schematically in the drawing by means of gates 16 and 17 which, respectively, control the outputs of the follow-up register Ri and the speed register Rv, as well as one controlled by the program (or interpolating) unit 2, so as to enable gate 16 only during rapid movements and gate 17 only during the working displacements when the speed should be relatively slow and controlled by the programmed (or computed) values introduced into the speed register Rv. Additionally the gate 17 is enabled by the signal 18 only when the contents of the register Ri are nil, while the gate 16 is enabled via line 19 by the presence of a nil speed command in the register Rv.
In this way, there is obtained a position error .epsilon. measured by the position error detector 7 which is always small, while the moving part can lag behind with respect to the position command even by several steps of the detector 7. The follow-up register allows the storage of a measure of the current position error to be utilized at the end of the positioning phase for arriving correctly at the predetermined target.