Patent Publication Number: US-2022212343-A1

Title: Operation command generation device, mechanism control system, non-transitory computer readable storage medium, operation command generation method, and mechanism control method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. 2021-001712, filed Jan. 7, 2021. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     Technical Field 
     The present invention relates to an operation command generation device, a mechanism control system, a non-transitory computer readable storage medium, an operation command generation method, and a mechanism control method. 
     Background Art 
     Japanese Patent Application Laid-Open No. H05-90386 shows a motor control device in a conveyance device that calculates a command value that satisfies a stroke and a movement time given from an interpreter with reference to one selected cam curve table from a cam curve memory provided with a plurality of types of cam curve tables. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, an operation command generation device includes movement curve designation circuitry configured to determine a movement curve describing an operation of each of at least one mechanism element included in a virtual mechanism, and operation command generation circuitry configured to generate an operation command to control an actual mechanism based on the movement curve. 
     According to another aspect of the present invention, a mechanism control system includes an operation command generation device and mechanism control circuitry. The operation command generation device includes movement curve designation circuitry configured to determine a movement curve describing an operation of each of at least one mechanism element included in a virtual mechanism, and operation command generation circuitry configured to generate an operation command to control an actual mechanism based on the movement curve. The mechanism control circuitry is configured to control the actual mechanism according to the operation command. 
     According to further aspect of the present invention, a non-transitory computer readable storage medium is configured to retrievably store a computer-executable program therein. The computer-executable program causing a computer to perform an operation command generation method. The method includes determining a movement curve describing an operation of each of at least one mechanism element included in a virtual mechanism, and generating an operation command to control an actual mechanism based on the movement curve. 
     According to the other aspect of the present invention, an operation command generation method includes determining a movement curve describing an operation of each of at least one mechanism element included in a virtual mechanism, and generating an operation command to control an actual mechanism based on the movement curve. 
     According to yet further aspect of the present invention, a mechanism control method includes determining a movement curve describing an operation of each of at least one mechanism element included in a virtual mechanism, generating an operation command to control an actual mechanism based on the movement curve, and outputting the operation command to the actual mechanism. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings. 
         FIG. 1  is a conceptual diagram illustrating a mechanism control system according to a preferred embodiment of the present invention and an actual mechanism controlled by the mechanism control system. 
         FIG. 2  is a diagram showing a configuration of a general computer as an example of a hardware configuration of the operation command generation device. 
         FIG. 3  is a conceptual diagram showing the relationship between the actual mechanism and the virtual mechanism handled by the operation command generation device. 
         FIG. 4  is a structural block diagram of the operation command generation device. 
         FIG. 5  is a diagram showing an example of a GUI presented to the user through the monitor by the movement curve designation part. 
         FIG. 6  is a conceptual diagram illustrating a method of generating an operation command by the operation command generation part. 
         FIGS. 7A and 7B  are diagrams for explaining an offset operation. 
         FIG. 8  is a diagram showing an example of a GUI presented to the user by the motor selection information output unit. 
         FIG. 9  is a diagram showing an example of a GUI for a user to select a model of an electric motor product, which is displayed by selecting a model designation section on the GUI of  FIG. 8 . 
         FIG. 10  is a diagram showing an example of a GUI through which a user selects a physical model. 
         FIG. 11  is an overall structural block diagram of the mechanism control system including the operation command generation device. 
         FIG. 12  is a diagram showing an example of a GUI on the operation terminal. 
         FIG. 13  is a flowchart showing a method of generating an operation command for the actual mechanism and a method of controlling the actual mechanism, which are executed by the mechanism control system. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     General-purpose industrial robots are widely used because they have a high degree of freedom of operation and can be widely applied to various automatic machines. On the other hand, the high degree of freedom of movement means that the programming of the industrial robot for specific applications requires technical knowledge specific to the industrial robot. 
     Incidentally, not all automatic machines widely used in the world are necessarily realized by general-purpose industrial robots, and there are many automatic machines realized by using a unique mechanical mechanism, for example, a cam mechanism or a link mechanism. It is considered that the introduction of an industrial robot to update such an aging automatic machine or the like brings about many advantages such as facilitation of maintenance due to commonality of equipment and coping with small-lot production of various products due to flexible change of an operation pattern. 
     However, since the operation realized by the unique mechanical mechanism is described based on the unique mechanical mechanism, the operation cannot be immediately transferred to the industrial robot, and since a technician who has expert knowledge of the industrial robot is required, the assets of automatic control which have been realized by the unique mechanical mechanism cannot be effectively utilized. 
     It is considered that this situation occurs not only in a general-purpose industrial robot but also in an attempt to realize an automatic control asset which is described based on a specific mechanism in another mechanism. 
       FIG. 1  is a conceptual diagram illustrating a mechanism control system  1  according to a preferred embodiment of the present invention and an actual mechanism  2  controlled by the mechanism control system  1 . In this example, the mechanism control system  1  includes an operation command generation device  3 , a mechanism control device  4 , and an operation terminal. 
     The actual mechanism  2  is a mechanical mechanism that automatically executes some work T. As shown in  FIG. 1 , the actual mechanism in the present embodiment is obtained by attaching an appropriate end effector to a general-purpose industrial robot, but the mechanical mechanism of the actual mechanism  2  is not necessarily limited. When an industrial robot is used, other types of robots, such as a horizontal articulated type (scalar type), a parallel link type, and an orthogonal type, may be used in addition to the vertical articulated robot as illustrated. Further, a general-purpose or dedicated mechanism other than the robot may be used. As the dedicated mechanism, a link mechanism, a cam mechanism, or a combination thereof is assumed. 
     In this example, the actual mechanism  2  includes an electric motor as its power source, and its operation is mainly performed by control of the electric motor. That is, the operation of the industrial robot constituting the actual mechanism  2  is realized by the servo motor installed in each joint. However, the actual mechanism  2  may include a power source other than the electric motor. For example, a pneumatic or hydraulic device or the like may be appropriately used for the operation of the end effector, or a part or all of a device other than an electric motor may be used as a power source of a mechanism other than the end effector of the actual mechanism  2 . 
     Further, the term “actual mechanism” is used in contrast to the term “virtual mechanism” which will be used later in this specification. Here, the “actual mechanism” means a mechanical mechanism that is actually constructed and used to execute the task T. On the other hand, the “virtual mechanism  7 ” means a mechanical mechanism which is virtually conceived as a mechanism for executing the work T and is not actually constructed and used. 
     The work T may be any work as long as it is automatically executed by the actual mechanism  2 . The contents of other operations T such as processing, transportation, inspection, and demonstration of an article are not limited. 
     The mechanism control system  1  is a single device or a system including a plurality of devices having a function of controlling the operation of the actual mechanism  2 . In the example shown in  FIG. 1 , the mechanism control system includes a mechanism control device  4  for supplying power to and controlling the actual mechanism  2 , an operation command generation device  3  for generating an operation command for the actual mechanism  2  and transferring the operation command to the mechanism control device  4  to control the actual mechanism  2 , and an operation terminal  5  for manually operating or stopping the actual mechanism  2  in an operational state or non-operational state and instructing change of the operating speed and direction thereof. It is shown that each device is independent and connected via electrical information communication respectively. 
     Here, since the actual mechanism  2  is an industrial robot, the mechanism control device  4  is a so-called robot controller. In addition to a servo controller that controls a servo motor included in the actual mechanism  2 , the mechanism control device  4  is provided with a control mechanism that electronically controls a pneumatic device and other various auxiliary devices in accordance with an operation command generated by the operation command generation device  3 . 
     In this example, a general computer is used as hardware of the operation command generation device  3 , and the computer is caused to function as the operation command generation device  3  by software executed on the hardware. The operation command generation device  3  generates an operation command which is a command group to be executed when the mechanism control device  4  controls the actual mechanism  2 . The user inputs the work T to be realized by the actual mechanism  2  to the operation command generation device  3  based on the virtual mechanism  7  as described later, and the operation command generation device  3  generates an operation command so that the work T thus input is realized by the actual mechanism  2 . The user&#39;s input and the generation of an operation command in the operation command generation device  3  will be described later in detail. 
     The operation terminal  5  is a device for an operator to instruct conditions at the time of execution, such as start and stop of execution of the work T, an execution speed, a direction, and the like, to the mechanism control device  4  in which an operation command is prepared and preparation for automatically executing the work T by the actual mechanism  2  is completed. The operation terminal  5  is not a device which is always necessary for the mechanism control system, and may be provided as necessary. The instruction to start and stop the automatic execution of the work T by the mechanism control device  4  and the timing thereof are not necessarily based on the instruction of the operator using the operation terminal  5 , and may be based on a signal from an upstream or downstream device (not illustrated) with respect to the mechanism control device  4 . 
     The hardware configuration of the mechanism control system  1  itself is not limited to the combination of the operation command generation device  3 , the mechanism control device  4 , and the operation terminal  5  illustrated in  FIG. 1 , and one device may have a plurality of functions of these devices, or vice versa. For example, the mechanism control device  4  may have a function as the operation command generation device  3 , or vice versa. In addition, in  FIG. 1 , the operation command generation device  3  and the mechanism control device  4  are illustrated to be capable of performing information communication with each other by wired connection, and the mechanism control device  4  and the operation terminal  5  are illustrated to be capable of performing information communication with each other by wireless connection, but a mode of the connection is not limited. The devices may be communicatively coupled via any telecommunications network, including the Internet. In addition, a part of the functions of the mechanism control system  1 , for example, the function as the operation command generation device  3  may be provided by so-called cloud computing via a telecommunication network. 
     Hereinafter, the operation command generation device  3  included in the mechanism control system  1  will be described in detail.  FIG. 2  is a diagram showing a configuration of a general computer  6  shown as an example of a hardware configuration of the operation command generation device  3 . In the computer  6 , a CPU (Central Processing Unit)  6   a  serving as a processor, a RAM (Random Access Memory)  6   b  serving as a memory, an external storage device  6   c,  a GC (Graphics Controller)  6   d,  input devices  6   e,  and I/Os (Input/Output)  6   f  are connected to each other via a databus  6   g  so as to be able to exchange electrical signals with each other. Note that the hardware configuration of the computer  6  shown here is an example, and a configuration other than this may be adopted. 
     The external storage device  6   c  may be a device capable of statically recording information, such as a hard disk drive (HDD) or a solid state drive (SSD). Signals from the GC  6   d  are output to a monitor  6   h,  such as a CRT (Cathode Ray Tube) or a so-called flat panel display, on which a user visually recognizes an image, and displayed as an image. The input devices  6   e  are one or more devices for a user to input information, such as a keyboard, a mouse, and a touch panel, and the I/O  6   f  are one or more interfaces for the computer  6  to exchange information with external devices. The I/O  6   f  may include various ports for wired connection and a controller for wireless connection. 
     A computer program for causing the computer  6  to function as the operation command generation device  3  is stored in the external storage device  6   c,  read by the RAM  6   b  as necessary, and executed by the CPU  6   a.  That is, a program code for causing the computer  6  to function as the operation command generation device  3  by being executed by the RAM  6   b  is stored in the CPU  6   a.  Such a computer program may be provided by being recorded on an appropriate computer-readable information recording medium such as an appropriate optical disk, a magneto-optical disk, or a flash memory, or may be provided via an external information communication line such as the Internet via I/O  6   f.    
       FIG. 3  is a conceptual diagram showing the relationship between the actual mechanism  2  and the virtual mechanism  7  handled by the operation command generation device  3 . Here, the virtual mechanism  7  is illustrated as a combination of a slider crank mechanism and a flat cam mechanism, but this is shown as a conceptual example, and differs depending on the work T desired by the user. 
     At this time, an operation necessary for the work T is determined for each mechanism element constituting the virtual mechanism  7 . For example, the links are designed so that the displacements of the sliders  7   a  are determined with the rotation of the crankshaft  7   b,  and the cam curves are designed so that the displacements of the tables  7   c  are determined with the rotation of the camshaft  7   d.  Power shafts such as a crankshaft  7   b  and a camshaft  7   d  of the virtual mechanism  7  operate in conjunction with rotation of virtual master shafts (sometimes referred to as “master cams” or the like in mechanism design). 
     Such a virtual mechanism  7  is conceived as a unique mechanical mechanism that realizes the task T. Therefore, the operation of each mechanism element of the virtual mechanism  7  has high affinity with each operation necessary for realizing the task T. That is, it is assumed that there is a good intuitive correspondence with each action of the task T. Alternatively, the virtual mechanism  7  may represent a mechanical mechanism itself of an automatic machine actually used in the past, and the operation of each mechanical element of the virtual mechanism  7  may be the operation of the mechanical mechanism of the automatic machine. 
     On the other hand, the actual work T is realized by the actual mechanism  2 . The actual mechanism  2  is usually different from the virtual mechanism  7  in mechanical mechanism, and in this example, the actual mechanism  2  is a general-purpose vertical articulated robot as shown in the figure. The actual mechanism  2  has multiple degrees of freedom (seven degrees of freedom in the illustrated example), and can reproduce the work T executed by the virtual mechanism  7  even though the mechanical mechanisms are different from each other. 
     At this time, the operation command to be given to the actual mechanism  2  in order to realize the work T must be in accordance with the mechanical configuration of the actual mechanism  2 . That is, in the example of  FIG. 3 , the task T must be described as an operation in the coordinate system of the actual mechanism  2  which is a vertical articulated robot. However, since the actual mechanism  2  is not a mechanical mechanism designed based on the work T, it is difficult to describe the operation included in the work T as the operation of the actual mechanism  2 . On the other hand, since the virtual mechanism  7  is a machine mechanism designed in accordance with the work T, it is easy to describe the work T as a set of operations of respective mechanism elements included in the virtual mechanism  7 , or the virtual mechanism  7  can be immediately obtained as an operation of a machine mechanism of an automatic machine actually used in the past. 
     The operation command generation device  3  is a device that generates an operation command for the actual mechanism  2  based on the work T described intuitively or expressed as an operation of each mechanism element included in the virtual mechanism  7  that already exists. Therefore, the operation command generation device  3  receives a description of an operation based on the virtual mechanism  7  as an input and outputs an operation command for the actual mechanism  2 . 
       FIG. 4  is a structural block diagram of the operation command generation device  3 . In a case where the operation command generation device  3  is realized by the general computer  6  illustrated in  FIG. 2 , each function illustrated in the drawing is realized by executing a computer program by the CPU  6   a,  allocating a storage area to the RAM  6   b  or the external storage device  6   c,  or the like. First, each structural block shown in  FIG. 4  will be briefly described, and then each function will be described in detail. 
     The movement curve designation part (movement curve designation circuitry)  30  is provided for the user to designate a movement curve describing the operation of one or more mechanism elements included in the virtual mechanism  7 . The movement curve designation part  30  includes a GUI (Graphical User Interface) for the user to designate a movement curve, and is configured to obtain a movement curve by the user inputting a unit movement curve obtained by designating a start point, an end point, and a curve shape, as will be described later. 
     The virtual mechanism information designation part  31  is provided to designate virtual mechanism information, and the designated virtual mechanism information is held in the virtual mechanism information holding part  32 . The virtual mechanism information includes at least a mechanical relationship between a plurality of mechanism elements. Qualitatively, the virtual mechanism information is a part or all of information necessary for converting the operation of the mechanism represented in the virtual mechanism  7  into the operation of the mechanism in the actual mechanism  2 . In the present embodiment, the virtual mechanism information includes variables for generating degrees of freedom in the virtual mechanism  7 , a relationship between the variables, and a relationship with coordinates in the actual mechanism  2 . A specific example of the virtual mechanism information will be described later. 
     The variables included in the virtual mechanism information may be designated by the virtual mechanism information designation unit  31  or may be designated by the movement curve designation part  30 . For example, if the user adds an “axis” on the GUI of the movement curve designation part  30 , since the “axis” is a variable with one degree of freedom to be included in the virtual mechanism information, the information of the “axis” may be sent to the virtual mechanism information designation part  31  and the corresponding variable may be added to the virtual mechanism information. Conversely, if a variable specifying the operation of a mechanism element included in the virtual mechanism  7  is added to the GUI of the virtual mechanism information designation part  31 , the variable is handled as an “axis” in the movement curve designation part  30 , and the information of the variable is to be sent to the movement curve designation part  30  and the information of the corresponding “axis” may be added to the movement curve designation part  30 . 
     The operation command generation part (operation command generation circuitry)  33  generates an operation command of the actual mechanism  2  based on the movement curve designated by the user in the movement curve designation part  30 . At this time, the operation command generation part  33  uses the virtual mechanism information held in the virtual mechanism information holding part  32 . Since the actual mechanism  2 , which is an industrial robot, can be operated by an operation command specifying target coordinates and an attitude in its coordinate space, i. e., a so-called robot coordinate system, the operation command generation part  33  can generate an operation command from the coordinates and the attitude to be taken by the actual mechanism  2  obtained using the movement curve and the virtual mechanism information. 
     When the actual mechanism  2  is not an industrial robot but another arbitrary mechanism, an operation command to be given to the actual mechanism  2  may not be immediately obtained only from the target coordinates and orientation. In such a case, the operation command generation part  33  generates an operation command by obtaining physical model information of the actual mechanism  2  described later from the physical model information holding part (a physical model information storage)  37 . 
     The generated operation command is output from the operation command output part  34  to the mechanism control device  4 . The mechanism control device  4  stores the operation command received from the operation command output part  34 , controls the actual mechanism  2  based on the operation command, and causes the actual mechanism  2  to perform the work T. 
     Further, the load variation calculation section (load variation calculation circuitry)  35  calculates a load variation of the electric motor included in the actual mechanism  2 , which is caused by the work T input by the user. Since this load variation depends on the specific configuration, shape, and weight of the actual mechanism  2 , the load variation calculation section  35  calculates the load variation of the electric motor based on the physical model information held in the physical model information holding part  37  in addition to the contents of the work T. The physical model information is designated by the user by the physical model information designation part  36 . The physical model information designation part  36  includes an appropriate GUI for the user to designate the physical model information. 
     The motor selection information output unit  38  outputs motor selection information indicating whether or not to select a motor based on the load variation calculated by the load variation calculation section  35 . This output is presented to the user through the monitor  6   h  of the computer  2 , for example, and provides information about the electric motor to be selected when the user constructs the actual mechanism  2  that realizes the work T. 
       FIG. 5  is a diagram showing an example of a GUI presented to the user through the monitor  6   h  by the movement curve designation part  30 . In the GUI shown in this example, a movement curve or the like can be input in a graph format in which the horizontal axis represents time and the rotation angle of the master shaft, and the vertical axis represents displacement of a mechanism element or changes in other specified items. Each element shown in the GUI will be described below. 
     The horizontal axis scale indicating the horizontal axis is indicated by both the time scale  30   a  and the master shaft rotation-angle scale  30   b  in the upper part of the GUI. The master shaft rotation angle scale  30   b  indicates a rotation angle of a virtual master shaft that repeatedly rotates, and the range thereof is 0° to 360°. The time scale  30   a  indicates the elapsed time corresponding to the master shaft rotation angle  30   b.  The correspondence relationship between the master shaft rotation angle scale  30   b  and the time scale  30   a,  that is, the time required for one rotation of the master shaft can be arbitrarily set. Further, in  FIG. 5 , the unit of the time scale  30   a  is represented by seconds (sec), and the unit of the master shaft rotation angle scale  30   b  is represented by degrees (deg), but these units may be arbitrarily changed. For example, the unit of the time scale  30   a  may be minutes, times, or days, and the unit of the master shaft rotation angle scale  30   b  may be radians (rad). 
     On the vertical axis, the GUI is designed so that the user can appropriately add designation items necessary for describing the task T. In the example of  FIG. 5 , breakpoints  30   c,  shafts  30   d  (crankshafts), external forces  30   e,  shafts  30   f  (camshafts), output signals  30   g  (end effectors), and input signals  30   h  (operation completion signals) are shown from the top. Since a name that is easily understood by the user can be assigned to the designated item as appropriate, the name shown in  FIG. 5  may be different from the name described here. The names shown in  FIG. 5  are indicated in parentheses in the above text. 
     First, the shafts  30   d  and  30   f,  which are “shafts”, will be described. The “shaft” mentioned here is a variable constituting the degree of freedom of the virtual mechanism  7 , and indicates displacement of a mechanism element of the virtual mechanism  7 . The unit of  30   d  and  30   f  shown in  FIG. 5  are assumed to be the slider crank mechanism of  FIG. 3  and the flat cam mechanism of  FIG. 3 , respectively, the displacements of the slider  7   a  and the stage  7   c  driven by the flat cam are shown, but when the mechanism element is a rotary body such as a turntable, the rotation angle may be used as the displacements. Of course, the unit of the displacements is arbitrary, and is not limited to millimeters (mm) shown for the shaft  30   d  and the shaft  30   f  in  FIG. 5 , and may be set arbitrarily. 
     In the designation item of “shaft”, the horizontal axis represents time or a master shaft rotation angle, and the vertical axis represents displacements, so that the user can designate a movement curve  30   i  indicating changes in displacements of the mechanism elements in the time direction using the GUI. Here, the movement curve  30   i  includes two kinds of movement curves, i.e., a unit movement curve  30   j  shown in the experiment and a connection movement curve  30   j  connecting the unit movement curves  30   k.    
     What is important when specifying the movement curve  30   i  in the movement curve designation part  30  is the displacements that must occur in the mechanism elements in order to realize the task T. Therefore, the movement curve designation part  30  is designed such that the user can construct the movement curve  30   i  without designating the shape of the movement curve  30   i  over the entire range of the movement curve  30   i  (that is, the range of the master shaft rotation angle from 0° to 360°). 
     That is, when the user specifies the unit movement curve  30   j  included in the movement curve  30   i,  the movement curve  30   i  is obtained. The unit movement curve  30   j  is a curve describing a change of the displacements of the mechanism elements from a certain initial value to a target value. The movement curve designation part  30  obtains the unit movement curve  30   j  by causing the user to designate the start point  30   l  and the end point  30   m  and the curve shape of the unit movement curve  30   j  connecting the start point  30   l  and the end point  30   m.  The start point  30   l  and the end point  30   m  specify time (or master shaft rotation angle) and displacements, respectively. The curve shape may be selected from various curve shapes prepared in advance by the movement curve designation part  30 , or may be freely designed by the user. 
     As the curve shape, a representative curve, for example, a trapezoidal acceleration curve or a curved acceleration curve (a so-called S-shaped acceleration curve) may be selectively prepared in advance, and a curve of displacement in a crank mechanism or a link mechanism may be arbitrarily selected. In addition to this, a GUI may be separately prepared to design an arbitrary cam curve, or an acceleration curve or a jerk curve may be designated so that the user can design an arbitrary curve. Further, it may be possible to import a curve designed by another software, for example, a dedicated software for designing a cam curve. 
     When the user designates a necessary unit movement curve  30   j,  a movement curve designation part  30  connects adjacent unit movement curves  30   j  so as to be continuous by a connection movement curve  30   k.  To be more specific, the connection movement curve  30   k  is a curve connecting the end point  30   m  of the previous unit movement curve  30   j  and the start point  30   l  of the next unit movement curve  30   j,  and its curve shape follows a predetermined shape, for example, a curve acceleration curve. The curve shape of the connection movement curve  30   k  may be arbitrarily set by the user. 
     Here, since the movement curve  30   i  is a repetition curve repeated in a predetermined cycle, that is, in a cycle in which the master shaft makes one rotation, the displacements at the start point and the end point must coincide with each other. Therefore, the movement curve designation part  30  connects the end point of the rearmost unit movement curve  30   j  designated by the user and the start point of the foremost unit movement curve  30   j  by the connection movement curve  30   k  so as to be continuous by repetition. 
     Further, an external force  30   f,  which is a designation item indicating the external force, may be provided for arbitrary “shaft”. The external force  30   f  is designation item that designate the external force acting on the associated “shaft”, here the shaft  30   d  located directly above. Specifically, if the “shaft” is a mechanism element, for example, a crank press, a press reaction force acts on the mechanism element, and if the mechanism element is an object that lifts and moves an article, gravity due to holding of the article acts on the mechanism element. Such external force  30  generated in accordance with the progress of the work T can be described in the external force  30   f.    
     Since the external force  30   f  is used to calculate the load fluctuation of the electric motor as will be described later, the designation of the external force is not essential when the load fluctuation is not calculated. Further, in the present embodiment, the direction of force designated by the external force  30   f  is the direction of “shaft” associated with the external force  30   f.  Therefore, if a force is specified in a certain time range, it means that a specified force acts on the “shaft” in the axial direction. Note that, in the present embodiment, the signs of the shaft  30   d  and the external force  30   e  coincide with each other, but the signs may be arbitrary. 
     The output signal  30   g  designate changes in signal output from the mechanism control device  4  to the outside with the progress of time, i. e., rotation of the master shaft. This signal indicates, for example, a high/low change in impedance of an external output contact of the mechanism control device  4 , and an external device connected to the contact performs an operation based on the signal output from the mechanism control device  4 . In this example, the virtual mechanism  7  of  FIG. 3  is instructed to switch the operation of the end effector (not illustrated), and a signal is output at the timing shown in  FIG. 5 . The output signals  30   g  are not limited to high/low binary signals as described herein, and may be continuous signals, for example, voltage signals that output digital values based on a specific protocol. 
     The input signals  30   h  are signals input to the mechanism control device  4  from an external device, for example, an upstream or downstream device that is to execute the work T in conjunction with the actual mechanism  2 , a sensor for detecting the state of the work T, or the like. The input signals  30   h  shown in  FIG. 5  are also described as indicating a high/low change in impedance of an external input contact included in the mechanism control device  4 . 
     Here, the values of the input signals  30   h  are also described with respect to time or the rotation angle of the master shaft, as are the output signals  30   g  and other specified items. However, since the input signals  30   h  indicate values input from an external device that is not under the control of the mechanism control device  4 , the timing at which the values change cannot be controlled by the mechanism control device  4 . Therefore, when the input signals  30   h  are described as if their values change at a certain time, such description does not mean that the values of the input signals  30   h  change at that timing. 
     The input signals  30   h  are understood to specify conditions for switching between performing and stopping control by the mechanism control device  4 . That is, although the control by the mechanism control device  4  progresses with time (or rotation of the master shaft) in the horizontal axis direction of  FIG. 5 , there is a case where it is necessary to wait for a condition for executing a specified operation to be satisfied when the specified operation is performed. For example, after it is confirmed that the carrying-in of the processing object from the upstream device is completed or the operation of the device necessary for the work T, for example, the discharge of a predetermined amount of the adhesive is completed, the next operation is performed. 
     The input signals  30   h  in  FIG. 5  are described as operation completion signals, and are signals indicating that operations of devices associated with some actual mechanism  2  have been completed or are in operation. At this time, the meaning of the description of the input signals  30   h  is input signal, the time (or rotation of the master shaft) is advanced and each mechanism element is operated as specified when the value of the external input matches the value specified as the input signal  30   h.  If the value of the external input does not match the value specified as the input signal  30   h,  the time (or rotation of the master shaft) is stopped and the process waits until the value of the external input matches the value specified as the input signal  30   h.  By making it possible to designate such input signals  30   h  as designation items, the operation command generation device  3  can generate an operation command that can be switched between executing and stopping based on an external input. 
     Further, the execution and stop of controlling by the mechanism control device  4  may be switchably designated without depending on an external input. The breakpoints  30   c  are designation items for designating a temporary stop position of control by the mechanism control device  4 . In the example of  FIG. 5 , breakpoints are designated at two locations indicated by numbers 1 and 2, but this is to temporarily stop the control by the mechanism control device  4  when the time (or rotation of the master shaft) advances and reaches the timing designated as a breakpoint. The stopped control can be resumed by an operation of the operation terminal  5  described later. 
     By appropriately specifying the breakpoint, when the work T is newly constructed or the contents of the work T are partially changed, the operation contents of each mechanism element included in the work T can be finely checked. If it is confirmed that there is no problem in the operation content of each mechanism element designated as the task T, the breakpoint may be deleted or invalidated as described later. 
     By using the GUI described above, the movement curve designation part  30  allows the user to describe the work T as a movement curve  30   i  based on the virtual mechanism  7  or an aggregate of other designation items without the need to specifically construct the virtual mechanism  7 . Therefore, it is possible to easily describe automatic control based on a virtual unique mechanical mechanism without requiring special knowledge unique to the actual mechanism  2 , here, an industrial robot. Further, when the virtual unique mechanical mechanism coincides with the existing unique mechanical mechanism, the assets of automatic control described based on the unique mechanical mechanism can be effectively utilized. 
     Returning to  FIG. 4 , the operation command generation part  33  will be described before the virtual mechanism information designation part  31  and the virtual mechanism information holding part  32 . As described above, the operation command generation part  33  generates an operation command of the actual mechanism  2  based on the movement curve designated by the user in the movement curve designation part  30 . That is, based on the movement curve  30   i  in  FIG. 5  specified for the virtual mechanism  7  in  FIG. 3  and other specified items, an operation command for the actual mechanism  2  in  FIG. 3  is generated. 
     The generation method itself does not have to be limited to a specific method. For example, if identity transformation for associating the state of a specific virtual mechanism  7  with the state of a specific actual mechanism  2  is clear, an appropriate operation command will be obtained by obtaining the state of the actual mechanism  2  based on the movement curve  30   i  shown in  FIG. 5  and other specified items and generating an operation command for commanding the state. Such a method is not denied at all. 
     However, the mapping from the state of the virtual mechanism  7  to the state of the actual mechanism  2  is not necessarily an injection and may not be clear. Therefore, the operation command generation part  33  according to the present embodiment generates an operation command by a method described below. 
       FIG. 6  is a conceptual diagram illustrating a method of generating an operation command by the operation command generation part  33 . In this method, each variable in the virtual mechanism  7  is converted into each variable in the actual mechanism  2  via a target point to obtain an operation command 
     First, as shown at the left end of  FIG. 6 , for the virtual mechanism  7 , a movement curve  30   i  is specified for each mechanism element included in the virtual mechanism  7 . On the other hand, first, a target value (x, θ) v in virtual mechanism coordinates V, which is a coordinate system for the virtual mechanism, is obtained by conversion  33   a.    
     The target value (x, θ) v indicates the position and orientation of the action end of the virtual mechanism  7  at a certain time tin a three dimensional space, and is a six dimensional value. The relationship for obtaining the target value (x, θ) v from the movement curve  30   i  is included in the virtual mechanism information holding part  32  as a component of the virtual mechanism information  32   a.  This relationship defines the mechanical relationship between the mechanical elements of the virtual mechanism  7 . Such a mechanical relationship is given, for example, as a relational equation for obtaining the target value (x, θ) v from the value of each movement curve  30   i  at a certain time t. 
     Since the target value (x, θ) v is obtained over the entire time range, a trajectory of the target value (x, θ) v in the virtual mechanism coordinates V is obtained. The trajectory of the target value (x, θ) v is a closed curve in the virtual mechanism coordinates V. 
     Subsequently, the target value (x, θ) v in the virtual mechanism coordinates V is converted into the target value (x, θ) r in the real mechanism two coordinates R by the conversion  33   b.  The real mechanism coordinate R is a coordinate system for the actual mechanism  2 , and if the actual mechanism  2  is an industrial robot, the real mechanism coordinate R may be a robot coordinate system. Since the conversion  33   b  is a simple coordinate conversion, this conversion may be a simple affine conversion, and an affine matrix A may be given. By this conversion  33   b,  the locus of the target value (x, θ) r in the actual mechanism coordinates R is obtained as a closed curve. 
     The affine matrix A may also be included in the virtual mechanism information holding part  32  as a component of the virtual mechanism information  32   a.  The transformation matrix A is information defining the relationship between the virtual mechanism  7  and the actual mechanism  2 . By using such information, the action of the action end described for the virtual mechanism  7  can be expressed as an action for the actual mechanism  2 . 
     Here, if the mechanism control device  4  allows the target value (x, θ) r for the time t in the actual mechanism coordinates R to be directly given as an operation command, the obtained target value (x, θ) r can be used to immediately generate an operation command for the actual mechanism  2 , and thus it is not necessary to perform inverse kinematics calculation  33   c  described below in the operation command generation part  33 . When a robot controller for controlling many general-purpose industrial robots is used, it is considered that the inverse kinematics calculation  33   c  is unnecessary. 
     However, the actual mechanism  2  is not necessarily limited to a general-purpose industrial robot, and even if an industrial robot is used, when a movable element is further provided in an end effector thereof, an operation command cannot be immediately obtained from the target value (x, θ) r. 
     Then, inverse kinematics calculation  33   c  is performed. In this calculation, a value  33   d  of a variable that determines the state of the actual mechanism  2  is obtained by performing an inverse calculation, a so-called inverse kinematics calculation, on the target value (x, θr. At this time, the relationship between the variables of the actual mechanism  2  necessary for performing the inverse kinematics calculation is included in the physical model information  37   a  held in the physical model information holding part  37 . Then, if the value  33   d  of the variable that determines the state of the actual mechanism  2  with respect to the time t is known, the operation command generation part  33  can easily generate the operation command of the actual mechanism  2 . 
     Since the target value (x, θ) r for the inverse kinematics calculation  33   c  is obtained from the target value (x, θ) r indicating the operation of the virtual mechanism  7 , the operation command generation part  33  generates an operation command using the inverse kinematics calculation  33   c  based on the operation of the virtual mechanism  7 . The target value (x, θ) r indicating the operation of the virtual mechanism  7  is obtained from the movement curve  30   i  of the plurality of mechanism elements of the virtual mechanism  7  and the mechanical relationship between the mechanism elements. 
     Therefore, the virtual mechanism information designation part  31  in  FIG. 4  designates, as the virtual mechanism information, a mechanical relationship between a plurality of mechanism elements of the virtual mechanism  7  and a relationship between the virtual mechanism  7  and the actual mechanism  2 . This designation method is arbitrary and is not particularly limited. These relationships may be input by an appropriate GUI, or a data file describing such relationships may be prepared according to a specific format, and such a file may be imported. The designated virtual mechanism information is held by the virtual mechanism information holding part  32  and used by the operation command generation part  33 . 
     The operation command output part  34  outputs the operation command generated by the operation command generation part  33  to the mechanism control device  4 . By executing such an operation command by the mechanism control device  4 , even if the actual mechanism  2  and the virtual mechanism  7  have different mechanical configurations, the work T described as that for the virtual mechanism  7  is realized by the actual mechanism  2 . 
     The physical model information held in the physical model information holding part  37  may further include a virtual model of a mechanical component constituting the actual mechanism  2  in addition to the relationship between variables of the actual mechanism  2  used for the inverse kinematics calculation described above. These relationships and virtual models are designated by the user using the physical model information designation part  36  by an arbitrary GUI or other method. 
     Here, in the operation command generated by the operation command generation part  33 , the start point  30   l  and the end point  30   m  of the unit movement curve  30   j  designated by the user can be offset based on an external input.  FIGS. 7A and 7B  are diagrams for explaining an offset operation. 
     The movement curve  30   i  shown in  FIG. 7A  is an enlarged view of a part of the movement curve  30   i  shown by the shaft  30   d  in  FIG. 5 . At this time, the mechanism elements indicated by the shaft  30   d  are designated to move from the start point  30   l  to the end point  30   m  as indicated by the unit movement curve  30   j  as shown in the figure. 
     Although the operation performed by the mechanism elements shown in the shaft  30   d  may be any operation, when the mechanism elements perform some operation, for example, gripping or processing, on the carried article, the ideal position of the start point  30   l  may be different from the position of the start point  30   l  shown in  FIG. 7A  due to various causes such as positioning accuracy and variation in shape at the time of carrying the article. There is a possibility that the ideal position of the start point  30   l  is different every time the operation T is repeated. 
     Therefore, for example, the position and shape of the carried article are acquired by an arbitrary external device, for example, an image processor using a range sensor or an image sensor, and an offset doff, which is a deviation from the start point  30   l  indicated in the movement curve  30   i,  is input to the mechanism control device  4  as an external input. 
     The movement curve designation part  30  can designate the external input as an offset value to the start point  30   l .  FIG. 7B  shows how the movement curve  30   i  changes when an offset value doff is input as such an external input. In  FIG. 7B , a dotted line indicates a movement curve  30   i  originally designated by the user in the movement curve designation part  30 , and a solid line or a broken line indicates an operation performed by the actual mechanism  2  based on an operation command generated by the operation command generation device  3 , which is converted into an shaft  30   d  and displayed. 
     As shown in  FIG. 7B , the start point  30   l  is offset from the position specified by the user by an externally input offset doff, and can be an ideal position for the task T. On the other hand, since no offset is designated for the end point  30   m,  there is no change from the position designated by the user, and the offset of the start point  30   l  does not affect the subsequent operation. 
     The shape of the unit movement curve  30   j  connecting the start point  30   l  and the end point  30   m  is recalculated so as to be the curve shape designated by the user. Similarly, the shape of the connecting movement curve  30   l  is recalculated so that the offset start point  30   k  and the previous position are connected. A curve shape specified in advance is also used for the curve shape of the connection movement curve  30   k.    
     That is, the shapes of the unit movement curve  30   j  or the connection movement curve  30   k  before and after the start point  30   l  for which the offset is designated are recalculated, and the shape of the movement curve  30   i  is changed so that the mechanism element continuously operates even if the offset is made. 
     In the above description, the offset is designated only for the start point  30   l , but it is naturally possible to designate the offset for the end point  30   m  in a similar manner. Further, the number of the start point  30   l  and the end point  30   m  for specifying the offset is not limited, and the offset may be specified for all the start point  30   l  and the end point  30   m.  If necessary, at least one of the start point  30   l  and the end point  30   m  may be offset based on an external input. 
     Returning to  FIG. 4 , the operation of the load variation calculation section  35  will be described. Although the load variation calculation section  35  calculates the load variation of the electric motor included in the actual mechanism  2  as described above, the movement curve  30   i  in  FIG. 5  specified by the user relates to the mechanism elements of the virtual mechanism  7 , and the actual mechanism  2  and the virtual mechanism  7  do not necessarily match each other, therefore it is difficult to directly obtain the load of the electric motor included in the actual mechanism  2  from the movement curve  30   i.  Further, since the external forces  30   e  designated by the user are also shown for the “axes” in  FIG. 5 , i. e., the mechanical elements of the virtual mechanism  7 , it is not directly known what kind of load acts on the electric motor included in the actual mechanism  2 . 
     Therefore, the load variation calculation section  35  uses various kinds of information obtained by the operation command generation part  33  to generate an operation command. To be specific, the value  33   d  of the variable that determines the state of the actual mechanism  2  shown in  FIG. 6  is used. This is nothing but an operation of the electric motor included in the actual mechanism  2 . 
     Further, the load variation calculation section  35  refers to the physical model information held in the physical model information holding part  37 . The physical model information includes a physical model of the actual mechanism  2 , and at least information such as the masses and moments of inertia of mechanisms driven by the electric motors included in the actual mechanism  2  and the reduction ratios of the electric motors. Therefore, a temporal change in torque acting on the electric motors can be calculated from these values and the operation of the electric motors. 
     When the actual mechanism  2  is a multi joint robot as shown in  FIG. 1  and the like, the moment of inertia of the tip portion driven by the electric motor used in the intermediate joint of the robot arm can change depending on the posture of the tip portion (for example, if the tip portion is extended, the moment of inertia is large, and if the tip portion is folded to be small, the moment of inertia is small). The physical model information may include information about the shapes and masses of the movable parts constituting the actual mechanism  2 , and the load variation calculation section  35  may obtain the moments of inertia by physical simulation based on the attitude of the actual mechanism  2 . Alternatively, the physical model information may include the masses of mechanisms driven by a certain motor and the maximum values of the moments of inertia, and the load variation calculation section  35  may calculate the torque acting on the motor using the maximum values of the moments of inertia. 
     For further accuracy, the load variation calculation section  35  calculates the influence of the external forces  30   e  specified by the user. As shown in  FIG. 5 , the external forces  30   g  specified by the user are specified for the direction of variation of the mechanism elements of the virtual mechanism  7 . 
     Therefore, the load variation calculation section  35  needs to indicate the external forces in the directions of variables that determine the state of the actual mechanism  2 . This method is substantially the same as the method of generating an operation command by the operation command generation part  33  shown in  FIG. 6 . 
     That is, the external forces specified by the user are obtained as the direction and magnitude in the virtual mechanism coordinates V by the conversion  33   a.  Further, the external forces indicated in the virtual mechanism coordinates V are obtained as the direction and magnitude in the real mechanism coordinates R by the conversion  33   b.  Further, from the values of the variables that determine the state of the actual mechanism  2  obtained by the inverse kinematics calculation  33   c,  the magnitudes of forces that the external forces at the real mechanism coordinates R at a certain time t exert on the variation directions of the variables that determine the state of the actual mechanism  2  can be calculated. Therefore, based on the magnitudes of the forces, torques due to the external forces acting on the motors included in the actual mechanism  2  can be obtained. 
     Finally, the load fluctuation of the electric motor included in the actual mechanism  2  can be obtained as the sum of the inertial torque obtained from the movement curve  30   i  and the physical model information designated by the user and the external torque obtained from the external force  30   e  designated by the user. 
     The motor selection information output unit  38  presents the load variation of the motor calculated by the load variation calculation section  35  to the user, and provides information about the motor to be selected.  FIG. 8  is a diagram illustrating an example of a GUI presented to the user by the motor selection information output unit  38 . 
     On the GUI, necessary information is presented to the user. The GUI includes a motor designation section  38   a  for indicating the presentation of the information about which motor among the motors included in the actual mechanism  2  and designating information about which motor the user ask for, a model designation section  38   b  for designating a model name of the motor selected for the designated motor and specifying a model of the motor by the user, a required specification display section  38   c  for displaying specifications required for the motor from the load variation of the motor calculated by the load variation calculation section  35 , a motor specification display section  38   d  for displaying specifications of the model of the motor currently selected, and a load variation display section  38   e  for displaying the load variation of the motor calculated by the load variation calculation section  35  as a locus on a graph. The type of information to be included in the GUI and the display method thereof are arbitrary. 
     In the motor designation section  38   a,  a motor is specified by an identification name for identifying a plurality of motors included in the actual mechanism  2 . The identification name may be specified by the physical model information. On the other hand, the specifications of the electric motor are not specified from this information. The user can select any of the electric motors included in the actual mechanism  2  by selecting the electric motor designation section  38   a  on the GUI. When a motor is selected, the display contents of the model designation section  38   b,  the required specification display section  38   c,  the motor specification display section  38   d,  and the load variation display section  38   e  are switched to those for the selected motor. 
     In the model designation section  38   b,  a model of a product selected as the selected electric motor is specified. The user can select a model of an actually available electric motor product by selecting the model designation section  38   b  on the GUI. The GUI for selecting the model of the electric motor product will be described later. The model designation section  38   b  specifies a specific model of the electric motor product used as the selected electric motor, thereby specifying specific specifications of the electric motor. 
     The required specifications display section  38   c  displays the required specifications of the selected electric motor based on the load fluctuation of the electric motor calculated by the load variation calculation section  35 . In the example of  FIG. 8 , the effective torque, the load ratio, the maximum torque, the maximum speed and the average speed are shown. The required specifications are information indicating that work T cannot be performed unless the selected electric motor has performance satisfying the required specifications. 
     In the electric motor specification display section  38   d,  the specifications of the model of the motor product selected for the selected motor are displayed. Regarding the information displayed at this time, the electric motor selection information output part (motor selection information output circuitry)  38  holds the models available to the user as a database in advance. Further, in the electric motor specification display section  38   d,  the electric motor specifications corresponding to the request specifications displayed in the required specification display portion  38   c  may be displayed in association with each other so that the user can easily compare the both. In the example of  FIG. 8 , the requirement specifications and the electric motor specifications in the correspondence relationship are shown adjacent to each other in the lateral direction to indicate that they correspond to each other. 
     Although the motor specifications must satisfy the required specifications, if the motor specifications do not satisfy the required specifications, the lacking motor specifications are highlighted as shown in  FIG. 8  to clearly indicate that the performance of the model of the motor product selected as the motor is lacking. By looking at such a display, the user can immediately understand that the model of the motor product currently selected needs to be changed. 
     The load fluctuation display section  38   e  graphically displays a locus of load variation that the selected electric motor receives when the actual mechanism  2  executes the work T. In the example of  FIG. 8 , a change in the operating state of the electric motor on a plane in which the horizontal axis represents the electric motor torque and the vertical axis represents the electric motor speed is indicated by a thick line. In this plane, a region  38   f  indicates an operating condition under which the motor can be operated steadily, a region  38   g  indicates an operating condition under which the motor can be operated non-steadily (short-time operation), and a region  38   h  indicates an operating condition under which the motor cannot be operated due to overloading. The operating condition under which the selected electric motor executes the work T can be clearly understood by looking at the locus shown in the plane. 
       FIG. 9  is a diagram showing an example of a GUI for a user to select a model of an electric motor product, which is displayed by selecting the model designation section  38   b  on the GUI of  FIG. 8 . On the GUI, each model of the electric motor product is displayed in an organized manner so that the user can easily grasp each model. In the example of  FIG. 9 , the electric motor products are classified into series  1  to series  4  and arranged. Such classification may be selected based on specifications, shapes, and the like of electric motor products so as to be easily understood by a user. 
     In addition, the displayed models are provided with different display modes. In the present embodiment, the display mode is made different by changing the display color, but how to make the display mode different is arbitrary. Further, in  FIG. 9 , in order to indicate the difference in color, the frames indicating the models are distinguished by being indicated by a thin line, a thick broken line, and a thick line. In this example, a thin line indicates red, a thick broken line indicates yellow, and a thick line indicates green. 
     The difference in the display mode is selected according to how much the specifications of each model of the electric motor product displayed on the GUI satisfy the required specifications of the electric motor obtained from the load variation of the electric motor calculated by the load variation calculation section  35 . That is, when the specifications of the electric motor product related to the displayed model satisfy all the required specifications (that is, when steady operation is possible), the color is green, when the required specifications are partially satisfied (that is, when operation is possible if unsteady operation is permitted), the color is yellow, and when the required specifications are not satisfied (that is, when operation is impossible), the color is red. 
     As described above, based on the load variation of the electric motor obtained for the task T, the electric motor selection information indicating whether or not the model of the electric motor product satisfies the required specifications, that is, whether or not the electric motor related to a specific model can be selected, is shown on the GUI for selecting the model of the electric motor product. Further, since the load variation display section  38   e  of  FIG. 8  shows changes in the operating state of the electric motor with respect to the operating conditions of the electric motor, it is easy to determine whether the actual mechanism  2  can be constructed at a lower cost by selecting, as the selected electric motor, a model of a high-performance electric motor product that can be operated under operating conditions that allow steady operation at all times or a model of an electric motor product that can be operated under operating conditions that allow unsteady operation. 
     When the user selects a model of a desired motor product on the GUI of  FIG. 9 , the model name displayed in the model designation section  38   b  of  FIG. 8  is changed, and accordingly, the motor specifications displayed in the motor specification display section  38   d  and the shapes of the regions  38   f,    38   g,  and  38   h  in the load variation display section  38   e  correspond to the selected model of the motor product. 
     Returning to  FIG. 4 , an example of the GUI of the physical model information designation part  36  will be described. The physical model information designation part  36  may be of any type as long as the user can designate information necessary as the physical model information described above. In the present embodiment, as an example of such a GUI,  FIG. 10  shows an example of a GUI in which a user selects a physical model. 
     In the GUI, candidates of a plurality of mechanisms having a high possibility of being used by the user as the actual mechanism  2  are shown as a list in advance. For example, if the user wants to use an industrial robot, the user may select a suitable mechanism from among the candidates displayed in the upper row, and if the user wants to use another mechanism, the user may select an appropriate mechanism from among the candidates displayed in the middle and lower rows. 
     The physical model information designation part  36  prepares physical model information in advance for a mechanism presented to the user as an option. Therefore, the user can easily designate the physical model information simply by selecting the presented mechanism or by requesting additional input such as dimensions and masses of necessary parts after selecting the mechanism. 
     The user may designate the physical model information by other methods. For example, a file describing the physical model information in accordance with a predetermined format or a three-dimensional model created by commercially available three dimensional CAD software may be imported as the physical model information. 
       FIG. 11  is an overall structural block diagram of the mechanism control system  1  including the operation command generation device  3  described above. In the mechanism control system  1 , an operation command generated by the operation command generation device  3  is sent to the mechanism control device  4  and held in the operation command holding part  40 . The mechanism control device  4  controls the actual mechanism  2  to execute the work T by causing the mechanism control part (the mechanism control circuitry)  41  to read and execute the operation command from the operation command holding part  40  and to output the control command to the actual mechanism  2 . 
     At this time, external input is received from various external devices  8  such as upstream and downstream devices and sensors, and execution and stop of control are switched based on an input signal included in the external input, or a control target position of the actual mechanism  2  is offset based on an offset distance included in the external input. 
     Further, the mechanism control part  41  may include an execution speed changeable part (execution speed changeable circuitry)  42  capable of changing an execution speed and a direction of control of the actual mechanism  2 , and a command from the user to the mechanism control part  41  itself or an instruction from the user to the execution speed changeable part  42  may be made by the operation terminal  5 . 
       FIG. 12  is a diagram illustrating an example of a GUI in the operation terminal  5 . The operation terminal  5  is a device used by a user to instruct start and stop of execution of the work T itself and an additional condition during execution, and a portable computer terminal such as a tablet PC, a touch panel product used for operation of industrial equipment, a dedicated switch board, or the like may be used as appropriate.  FIG. 12  shows a case where a tablet PC is used as the operation terminal  5 . 
     In the GUI shown in  FIG. 12 , an execute button  5   a,  a stop button  5   b,  a reverse direction execute button  5   c,  a speed multiplying factor setting unit  5   d,  and a breakpoint enable/disable switching unit  5   e  are prepared. 
     The execute button  5   a  is an interface for instructing the actual mechanism  2  to execute the work T by the mechanism control part  41 . When the user selects the execute button  5   a,  the mechanism control part  41  starts the operation of the actual mechanism  2 , and the work T is repeatedly executed. The stop button  5   b  is an interface for instructing to stop the work T. When the user selects the stop button  5   b,  the mechanism control part  41  immediately stops the operation of the actual mechanism  2  being executed at that time point. The operation is resumed by selecting the execute button  5   a  again. Further, the operation of the actual mechanism  2  stopped by the arrival of the aforementioned breakpoint is also resumed by selecting the execute button  5   a.    
     The reverse direction execute button  5   c  is an interface for instructing the actual mechanism  2  to execute the work T in the reverse direction by the mechanism control part  41 . That is, the operation of the actual mechanism  2  based on the reverse direction execute button  5   c  is performed so as to trace back the time (or the rotation angle of the master shaft) shown in  FIG. 5  in the reverse direction. That is, each operation of the task T shown in  FIG. 5  is executed so as to proceed from right to left in the drawing. 
     The speed of the operation of the actual mechanism  2  in the forward direction or the reverse direction by the execute button  5   a  and the reverse direction execute button  5   c  can be changed by setting the speed magnification using the interface of the magnification designation part  5   d.  That is, when 100% is designated as the speed magnification, the work T is executed at the speed as designated by the user in  FIG. 5 , whereas if 50% is designated, the operation is performed slowly at half the speed, and if 200% is designated, the operation is performed at high speed at double the speed. 
     The direction and speed of the operation of the actual mechanism are changed by an execution speed changeable part  42 . An executing speed variable part  42  overwrites a control command outputted from a mechanism control part  41  to an actual mechanism  2  so as to operate at a speed multiplied by a speed magnification designated by a magnification designation part  5   d,  and sets the direction of operation by the control command and the executing order of operation commands to a forward direction or a reverse direction according to the direction of operation by selection of an execute button  5   a  and a reverse direction execute button  5   c.    
     Further, the breakpoint enable/disable switching unit  5   e  enables the user to select whether to enable or disable the stop of the operation of the task T by the breakpoints described with reference to the breakpoints  30   c  in  FIG. 5 . That is, when the enable is selected by the breakpoint enable/disable switching unit  5   e,  the mechanism control device  4  stops the operation of the work T in accordance with the command of the breakpoint included in the operation command. On the other hand, that is, when disable is selected by the breakpoint enable/disable switching unit  5   e,  the mechanism control device  4  ignores the command of the breakpoint included in the operation command. 
     Thereby, when operating the actual mechanism  2  first time, the actual mechanism  2  is stopped at the breakpoint as specified in advance and it is possible to confirm the whole operation of the work T by confirming the execution contents. On the other hand, by selecting disable in the breakpoint enable/disable switching unit  5   e  after confirming the operation, the work T can be continuously executed without removing the designated breakpoint and recreating the operation command and without stopping the operation at the breakpoint. 
       FIG. 13  is a flowchart showing a method of generating an operation command for the actual mechanism  2  and a method of controlling the actual mechanism  2 , which are executed by the mechanism control system  1 . 
     First, in step S 1 , virtual mechanism information is designated in advance. This is realized by the virtual mechanism information designation part  31  already described with reference to  FIG. 4 . In the following step S 2 , physical model information is designated. This is also realized by the physical model information designation part  36  described with reference to  FIG. 4 . 
     Then, in step S 3 , a movement curve is specified. This may be performed as described with reference to  FIG. 5  using the movement curve designation part  30  shown in  FIG. 4 . After the maintenance curve is specified, an operation command is generated in step S 4  based on the movement curve. This operation command is generated by the operation command generation part of  FIG. 4  by the method described with reference to  FIG. 6 . 
     Steps S 1  to S 4  thus far show how to generate an operation command for the task T. Further, control methods of the actual mechanism  2  are shown up to step S 8 . 
     In step S 5 , the load fluctuation of the electric motor included in the actual mechanism  2  is calculated based on the specified physical model information  37   a.  This calculation is performed by the load variation calculation section  35  described with reference to  FIG. 4 . Based on the calculated load variation, motor selection information is output in step S 6  and presented to the user. The user selects an appropriate electric motor based on the electric motor selection information and constructs the actual mechanism  2 . 
     In step S 7 , the operation command generated in step S 4  is output to the mechanism control device  4 . Finally, in step S 8 , the mechanism control device  4  controls the constructed actual mechanism  2  based on the operation command, so that the work T is realized. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.