Patent Publication Number: US-6341569-B2

Title: Sewing machine having means for estimating mass of sewing material

Description:
This application is based on and claims priority under 35 U.S.C. § 119 with respect to Japanese Application No. 2000-080468 filed Mar. 22, 2000 and Japanese Application No. 2000-390722 filed Dec. 22, 2000, the entire contents of both applications are incorporated herein by reference. 
     BACK GROUND OF THE INVENTION 
     1. Field of the invention 
     This invention relates to a sewing machine. 
     2. Description of related arts 
     An embroidery sewing machine, as an example of a conventional sewing machine, will be described as follows: An embroidery sewing machine comprises a) a frame holder holding an embroidering frame to restrain the cloth to be embroidered, b) an electric motor transferring the frame holder during embroidering, c) a needle driver for driving a sewing needle, and d) a controller for intelligently regulating the electric motor and the needle driver. Recently, an improved embroidery sewing machine works more accurately. The mass of the cloth, restrained on the embroidering frame, is varied. Furthermore, it is possible to attach a variety of embroidering frames, having different masses, to the sewing machine. Thus the various masses of the cloth and the various masses of the embroidering frame have a large influence on the sewing accuracy of the embroidery sewing machine. If the masses of the cloth and the embroidering frame are large, a fast embroidering speed vibrates the embroidery sewing machine and sags the embroidering frame because of a larger inertia thereof. 
     Thus improvement in embroidering accuracy of the embroidery sewing machine is limited. 
     To overcome the above problem, a conventional embroidery sewing machine comprises a setting means enabling selection of either a small mass material embroidering mode or a large mass material embroidering mode. The small mass material embroidering mode is one embroidering mode for cloth having a small mass. The large mass material embroidering mode is the other embroidering mode for cloth having a large mass. A person operating the embroidery sewing machine first decides whether the cloth to be embroidered has a large mass or not, and second inputs either the small mass embroidering mode or the large mass embroidering mode into the setting means for embroidering accuracy. If the cloth to be embroidered has a small mass, then the controller regulates the sewing machine to embroider at a rapid speed depending on the embroidering mode input by the person. If the cloth to be embroidered has a large mass, then the controller regulates the sewing machine to embroider at a slow speed. However, it is impossible for the person to accurately select whether the cloth has a large mass or not based upon eyesight. Both a material of the cloth (i.e. soft or stiff) and a condition for restraining the cloth on the embroidering frame (i.e. the cloth having a freely swingable portion extending off the embroidering frame) influence an inertia of the embroidering frame. Accordingly, if the person confirms the mass of the cloth only by eyesight, and determines whether the cloth is embroidered in the larger mass embroidering mode or the small mass embroidering mode, the selection of embroidering modes is not accurately suitable to the inertia of the embroidering frame, thus limiting any improvement in embroidering accuracy. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved sewing machine. 
     It is another object of the present invention to provide an improved sewing machine which obviates the above conventional drawbacks. 
     It is a further object of the present invention to provide a sewing machine which can estimate the mass of the material to be sewn. The sewing machine can accurately move the material, thereby providing a suitable sewing condition according to the mass of the material, and thereby obtaining sufficient embroidering accuracy. 
     In accordance with a first aspect of this invention, a sewing machine comprises a movable holder portion for holding a material to be sewn, a holder drive portion for moving the holder portion during sewing of the material, a needle drive portion for driving a sewing needle to sew, and a controller for regulating the holder drive portion and the needle drive portion. The controller includes an initial motion means for moving the material to be sewn before sewing or in an initial stage of sewing, and an estimating means for estimating a mass of the material depending on a physical value such as a moving speed of the material or a moving distance of the material for a predetermined period of time. 
     In accordance with a second aspect of this invention, the sewing machine further comprises an estimated mass adaptive control means for automatically adjusting a control mode based on the estimated mass of the material by the estimating means. 
     In accordance with a third aspect of this invention, the sewing machine determines the physical value based upon a driving speed of an initial movement of the movable holder portion holding the material or a driving distance of the holder drive portion for the predetermined period of time. 
     Thus, the present invention has the following advantages. In the sewing machine of this invention, before sewing or at the initial stage of sewing, the holder portion holding the material to be sewn is initially moved by the initial motion means. In the initial moving of the holder portion, the estimating means estimates the mass of the material to be sewn depending on the physical value of at least one of the moving velocity of the material and the moving distance of the material. Under the same conditions as the holder portion and the holder drive portion before the initial moving thereof, when the material is moved slowly during the initial moving, the estimating means determines the mass of the material to be large. When the material is moved rapidly during the initial moving, the estimating means determines the mass of the material to be small. 
     Also, under the same conditions of the holder portion end the holder drive portion before the initial moving thereof, when the moving distance within a predetermined amount of time is small, the estimating means determines the mass of the material to be large. When the moving distance within the predetermined amount of time is large, the estimating means determines the mass of the material to be small. Since mass generally corresponds to weight, the weight of the material is automatically determined based upon the mass of the material. 
     The sewing machine of this invention can automatically adjust a sewing condition thereof depending on the mass of the material estimated by the estimating means. 
     Thus accuracy of sewing, such as embroidering, can be kept independently of the mass of the material on the holder portion. 
     The sewing machine of this invention comprises the estimated mass adoptive control means which automatically determines the optimal control mode for regulating the holder drive portion. The estimated mass adoptive control means determines the optimal control mode depending on the mass of the material estimated by the estimating means. The estimated mass adoptive control means finds the optimal control mode for the holder drive portion and sets a constant for regulating the holder drive portion. The constant is optimally set (for accurately positioning the holder portion within a short response time) due to being precisely analyzed. When the mass of the material is large, the holder drive portion is driven slowly by the control mode set by the estimated mass adoptive control means. When the mass of the material is small, the holder drive portion is driven rapidly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will become more apparent from the following embodiment of the intention with reference to the attached drawings in which: 
     FIG. 1 shows a block diagram of a sewing machine of an embodiment of this invention having an embroidery function; 
     FIG. 2 shows a block diagram of a controller of the sewing machine of the embodiment; 
     FIGS.  3 (A) and  3 (B) show waves of initial motion command signals of the embodiment for initially moving a cloth holder holding a material to be embroidered; 
     FIGS.  4 (A) and  4 (B) show waves of rotation velocity of an electric motor of the embodiment initially moving a cloth holder holding the material, these waves output by an encoder; 
     FIG. 5 shows a graph conceptually representing a measured rotation amount and a standard rotation amount of the electric motor of the embodiment initially transferring the cloth holder holding the material; 
     FIG. 6 shows a graph conceptually representing a measured rotation velocity and a standard rotation velocity of the electric motor of the embodiment for initially moving the cloth holder holding the material; 
     FIG. 7 shows a map  1  representing a suitable control mode for an estimated mass of the material; 
     FIG. 8 shows a map  2  representing embroidery data which is suitable to the control mode; 
     FIG.  9 (A) shows a graph representing the measured rotation velocity of the electric motor of the embodiment actually moving the material having the small mass, and 
     FIG.  9 (B) shows a graph representing the measured rotation amount of the electric motor of the embodiment actually moving the material having the small mass; 
     FIG.  10 (A) shows a graph representing the measured rotation velocity of the electric motor actually moving the material having the large mass, and FIG.  10 (B) shows a graph representing the measured rotation amount of the electric motor actually moving the material having the large mass; 
     FIG. 11 shows a main flow chart diagram for a controller processing of the embroidery sewing machine of the embodiment; 
     FIGS.  12 (A) and  12 (B) show a main flow chart diagram for an X frame drive controller which processes the embroidery sewing machine of the embodiment; 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A sewing machine comprises a) a movable frame holder which supports an embroidering frame restraining a material to be sewn, b) a frame holder driver which transfers the frame holder, c) a needle driver which drives a sewing needle, and d) a controller which intelligently regulates the frame holder driver and the needle driver. During a sewing operation without the frame, such as when an embroidering frame is attached to the frame holder, the mass of the material to be sewn is generally directly equal to the mass of the cloth to be sewn. During another sewing operation when the frame such as the embroidering frame is on the frame holder, the material mass is equal to the mass of the cloth to be restrained by the frame holder, or is sometimes equal to the sum of the mass of the cloth and the mass of the frame holder. If accessories such as buttons are attached to the material, the mass of the material means the mass of the cloth together with the accessory. 
     The controller comprises an initial motion means, an estimating means, and an estimated mass adaptive control means. The initial motion means moves the frame holder with the material during an initial stage of the sewing operation. The estimating means estimates the mass of the material depending on a physical value which is at least one of a velocity of the material during the initial stage of the sewing operation and a moving distance of the material for a predetermined period of time. The estimated mass adaptive control means determines a control mode for regulating the frame holder driver depending on the material mass estimated by the estimating means. The initial motion means, the estimating means and the estimated mass adaptive control means are formed by either a set of a micro computer and a program or an electrical circuit. As the physical value for the moving speed and the moving distance of the material for the predetermined period of time, at least one of a driving speed of the frame holder driver during the initial stage of the sewing operation and a driving distance per unit time of the frame holder driver is suitable. When the frame holder driver is dominantly driven by an electric motor, either a driving speed of the electric motor (a rotation velocity of the electric motor) or a driving distance of the electric motor (a rotation amount of the electric motor) is suitable. In addition, the sewing machine of this invention further comprises a display means for showing the material mass which is estimated by the estimating means. In this case, a person operating the sewing machine can visually confirm the estimated material mass. The person can also manipulate the parameters to adjust a sewing operation mode and a sewing condition. 
     FIG.  12 (A) shows a typical main block diagram which is related to the controller of an embodiment of this invention. The sewing machine shown in FIG.  12 (A) comprises the electric motor as the frame holder driver which moves the frame holder holding the material to be sewn. During the sewing operation, a motor operation signal K 1  is sent to the electric motor, whereby the frame holder with the material is moved. The needle driver is also moved together with the frame holder, then the sewing operation such as embroidering is performed. An initial motion means sends an initial motion command signal K 2  to the electric motor before the sewing operation or during the initial stage of the sewing operation, whereby the frame holder is previously or initially moved. In the above process, a motor velocity signal K 3  and the initial motion command signal K 2  are input to a disturbance estimation portion. The motor velocity signal K 3  is received by a motor velocity detection means (.i.e. an encoder). The disturbance estimation portion shown in FIG.  12 (B) comprises a) a disturbance observer estimating a disturbance of the electric motor depending on the initial motion command signal K 2  and the motor velocity signal K 3 , and b) a digital filter sampling a signal having a desirable frequency. The motor velocity signal K 3  corresponds to the physical value of the driving velocity of the frame holder driver. The disturbance estimation portion estimates a disturbance of the electric motor depending on the motor velocity signal K 3  and the initial motion command signal K 2 , thereby estimating a change of the material mass. The disturbance estimation portion sends an estimated disturbance signal K 5  to an estimated mass processing portion. The estimated mass processing portion transforms the estimated disturbance signal K 5  into the physical value corresponding to mass, thereby outputting an estimated disturbance signal K 6 . When the material mass is varied, the, estimated disturbance signal K 5  is varied resulting from the material mass, and then the estimated disturbance signal K 6  is varied. In the above system, the disturbance estimation portion and the estimated mass processing portion are formed by programs operating a CPU. 
     The embodiment of this invention will be described as follows referring to the attached drawings. 
     FIG. 1 shows a block diagram of the embroidery sewing machine. An X-axis direction indicates one direction of a horizontal plane of the embroidery sewing machine. A Y-axis direction indicates the other direction of the horizontal plane. A Z-axis direction (a Z 1  direction and a Z 2  direction) indicates a vertical direction of the embroidery sewing machine. As shown in FIG. 1, the embroidery sewing machine comprises a needle bar  11  holding a sewing needle  10 . The needle bar  11  is swingable movable in the Z-axis direction (a Z 1  direction and a Z 2  direction). A top shaft  12  is rotatably provided at an upper portion of the embroidery sewing machine. A cam system  13  is disposed between the top shaft  12  and the needle bar  11 . The cam system  13  transforms the rotation of the top shaft  12  into the vertical reciprocating motion of the needle bar  11 . A top shaft motor  14  as a servomotor, rotates the top shaft  12 . A drive belt  15  transmits a driving force of the top shaft motor  14  to the top shaft  12 . A holder  17  is detachably holding the material  16  to be sewn (the material of this embodiment includes an embroidering frame  16   a  and a cloth  16   c  detachably attached to the embroidering frame  16   a ). A frame drive system  17   c  moves the holder  17  in the X-axis direction and in the Y-axis direction. An X-motor  18 , as a servomotor, transfers the holder  17  with the material  16  in the X-axis direction via the frame drive system  17   c . A Y-motor  19 , as another servomotor, transfers the holder  17  with the material  16  in the Y-axis direction via the frame drive systems  17   c . A controller  20  intelligently regulates the top shaft motor  14 , the X-motor  18  and the Y-motor  19 . Since the top shaft motor  14  is a driver activating the needle  10 , the top shaft motor  14  corresponds to a needle drive portion. Since both the X-motor  18  and the Y-motor  19  are actuators, the motors transfer the holder  17  holding the material  16 . Reference number  29  is a first motor position/velocity measuring portion which will be further described below. 
     FIG. 2 shows a block diagram of the controller  20 . The controller  20  comprises a) a console  21  which can be manipulated by a user, b) an embroidering command operator  22  which includes a main CPU and a memory 22m, c) a top shaft controller  23  which operates the top shaft  12 , d) a Y controller  24  which operates the travel amount of the frame holder  17  in the Y-axis direction, and e) an X controller  25  which operates the travel amount of the frame holder  17  in the X-axis direction. The embroidering command operation  22  outputs commands Pz, Py and Px to the top shaft controller  23 , the Y controller  24  and the X controller  25 , respectively. As shown in FIG. 2, the top shaft controller  23  comprises a top shaft drive controller  27 , a Z driver circuit  28  and a first motor position/velocity measuring portion  29 . As shown in FIG. 2, the top shaft drive controller  27  includes a first auxiliary CPU operated by the command Pz from the console  21 . The first motor position/velocity measuring portion  29  detects the rotation velocity and the motor position of the top shaft motor  14 , and sends a signal Mz as a first feedback signal to the top shaft drive controller  27 . The Y controller  24  comprises a Y frame drive controller  31 , a Y driver circuit  32  and a second motor position/velocity measuring portion  33 . The Y frame drive controller  31  includes a second CPU operated by the command Py from the console  21 . The second motor position/velocity measuring portion  33  detects the rotation velocity and the motor position of the Y motor  19 , and sends a signal My as a second feedback signal to the Y frame drive controller  31 . The X controller  25  comprises an X frame drive controller  41 , an X driver circuit  42  and a third motor position/velocity measuring portion  43 . The X frame drive controller  41  includes a third auxiliary CPU operated by the command Px from the console  21 . The third motor position/velocity measuring portion  43  detects the rotation velocity and the motor position of the X motor  18 , and sends a signal Mz as a third feedback signal to the X frame drive controller  41 . The first motor position/velocity measuring portion  29  is formed of a first increment encoder attached to the top shift motor  14 . The second motor position/velocity measuring portion  33  is formed of a second increment encoder attached to the Y motor  19 . The third motor position/velocity measuring portion  43  is formed of a third increment encoder attached to the X motor  18 . The X frame drive controller  41  comprises the memory 41m into which a program, corresponding to both the disturbance estimation portion and the estimated mass processing portion (as shown FIG.  12 ), is loaded. Thus, the X frame drive controller  41  has a function of assembling functions of the disturbance estimation portion and the estimated mass processing portion. The disturbance estimation portion is formed of the program including a) the disturbance observer which estimates the disturbance amount of the electric motor and b) the digital filter which samples the signal having a predetermined frequency. Thus, the X frame drive controller  41  sends the estimated disturbance signal K 6  to the main CPU of the embroidering command operator  22 . The embroidering command operator  22  also comprises a display  60  as shown in FIG.  2 . The display  60  shows the estimated mass of the material  16  depending on the signal from the embroidering command operator  22  so that a user can visibly confirm the estimated mass of the material  16 . 
     Prior to the embroidering operation as a typical sewing operation, the user sets the material  16  on the frame holder  17 . A thread is inserted into the sewing needle  10  held by the needle bar  11 . As the Y motor  19  is driven, then the material  16  with the frame holder  17  are moved in the Y-axis direction. As the X motor  18  is driven, then the material  16  and the frame holder  17  are moved in the X-axis direction. Accordingly, a horizontal motion of the material  16  held by the frame holder  17  is composed of the motions in the X-axis direction and the motions in the Y-axis direction. The top shaft  12  is driven by the top shaft motor  14 , thereby bringing the sewing needle  10  into the vertical reciprocating motion, thereby embroidering. 
     Prior to the above embroidering, the frame holder  17  is initially moved together with the material  16  by the electric motor receiving the command from the controller  20 . Then, the mass of the material  16  is estimated by the moving distance thereof during the initial stage of the embroidering. 
     The material mass estimation will be described as follows: In this embodiment, the material mass is estimated by driving the X motor  18 . In this material mass estimation, an initial motion command signal A 1  having a triangular pulse as shown in FIG.  3 (A) is first input to the X motor  18 . In FIG. 3, the horizontal axis represents time, and the vertical axis represents an electric voltage or current charged to the X motor  18 . The initial motion command signal A 1  comprises a first pulse (the electric voltage or current charged to the X motor) which gradually increases depending on time and a second pulse which gradually decreases (the electric voltage or current). Thus the initial motion command signal A 1  shows an increment, depending on time, and a decrement. As the initial motion command signal A 1  is input to the X motor  18 , the material is initially moved in the X-axis direction. Then the motor velocity signal K 3  which is monitored by the motor velocity detection means (the third motor position/velocity measuring portion  43 ) and the initial motion command signal A 1  (K 2  in FIG. 12) are input to the disturbance observer. Depending on a signal input to X motor and the motor velocity signal K 3 , the disturbance observer estimates the disturbance of the X motor  18 , and sends estimated disturbance signals as results of the motion operation to the digital filter. The digital filter samples an estimated signal having a predetermined frequency. Furthermore, the digital filter calculates a disturbance W 1  at a predetermined time, a maximum disturbance W 2  within a predetermined amount of time, and a cumulative disturbance W 3  within the predetermined amount of time. After that the digital filter selects the most suitable disturbance from the disturbance W 1  at a predetermined time, the maximum disturbance W 2  within a predetermined amount of time, and the cumulative disturbance W 3  within the predetermined amount of time. The estimated mass processing portion, as a program loaded on the X frame drive controller  41 , transforms the disturbance into a value corresponding to the mass of the material, and sends the value as the estimated disturbance signal K 6  to the embroidering command operator  22 . The mass of the material  16  is estimated in the above steps. The weight of the material  16  is automatically found by estimating the mass of the material  16 . 
     Another example of the material mass estimation will be described as follows: As the initial motion command signal A 1  is input to the X motor to be driven, then the material  16  is initially moved by the X motor. If the material mass equals a standard mass, the X motor outputs a standard characteristic pulse B 1  as shown in FIG.  4 (A). The horizontal axis represents time, the vertical axis represents the rotation velocity of the X motor in FIG.  4 (A). If the material mass differs from the standard mass, the X motor outputs a signal characteristic pulse C 1  differing from the standard characteristic pulse B 1 . Even though the same initial motion command signal A 1  is input to the X motor, when the material mass is larger than the standard mass, the, rotation velocity of the X motor falls. When the material mass is smaller than the standard mass, the rotation velocity of the X motor is raised. 
     The embroidering command operator  22  actually measures a motor position Sm (measured motor position Sm) of the X motor  18  at the predetermined time TO (FIG. 5) depending on a measurement signal Mx. The measurement signal Mx is sent from the third motor position/velocity measuring portion  43  (the third increment encoder). The above motor position is defined as a position of a rotor of the X motor  18 . The motor position of the X motor  18  relates to a driving distance of the X motor  18 . The measurement signal Mx corresponds to a physical value such as the driving distance of the motor  18 . A standard motor position S 0  within the predetermined amount of time T 0  of the X motor  18  is previously stored in either the memory 41 m of the X frame drive controller  41  or the memory 21 m of the embroidering command operator  22 . The standard motor position S 0  is defined as the motor position of the X motor  18  when the standard mass is moved by the X motor  18  upon receiving the initial motion command signal A 1 . The embroidering command operator  22  compares the measured motor position Sm and the standard motor position S 0  in order to calculate a deviation of rotation amount ΔSa, thereby finding the estimated mass of the material  16  by using a predetermined formula and its variable the deviation ΔSa. The deviation ΔSa is related to the weight of the material. Thus, in this embodiment, the mass of the material  16  is estimated via the weight of the material  16 . The weight of the material  16  is automatically found by estimating the mass of the material  16 . 
     The material mass can also be estimated from the rotation velocity of the X motor  18  instead of the motor position of the X motor  18 . The embroidering command operator  22  actually measures a rotation velocity Sp (a measured rotation velocity Sp) of the X motor  18  at a predetermined time T 1  (FIG. 6) depending on a motor speed signal which corresponds to a physical value relative to the driving speed of the X motor  18 . The motor speed signal is sent from the third motor position/velocity measuring portion  43 . A standard rotation velocity S 00  of the X motor  18  at the predetermined time T 1  is previously stored in either the memory 41 m of the X frame drive controller  41  or the memory 21 m of the embroidering command operator  22 . The standard rotation velocity S 00  is defined as the rotation velocity of the X motor  18  when the standard mass is moved by the X motor  18  upon receiving the initial motion command signal A 1 . The embroidering command operator  22  compares the measured rotation velocity Sp and the standard rotation velocity S 00  in order to calculate a deviation of rotation velocity ΔSb, thereby finding the estimated mass of the material  16  by using another predetermined formula and its variable the deviation ΔSb. The deviation ΔSb is related to the weight of the material  16 . Thus, in this embodiment, the mass of the material  16  is estimated via the weight of the material  16 . When the material  16  weight is found by the estimated mass of the material  16 , then the X frame drive controller  41  or the embroidering command operator  22  determines the weight of the material by using another predetermined formula depending on the estimated mass of the material  16 . 
     In this embodiment, it is preferable to determine the control mode for regulating the holder drive portion which moves the material  16  depending on a mapping mode. In the mapping mode, map  1  is formed by data representing relationships between an estimated mass and operation modes. A map  2  is formed by data representing relationships among the revolution numbers of the top shaft  12 , control modes for controlling moving velocities of an embroidering frame and these above operation modes. The map  1  and the map  2  are previously stored in either the memory 41 m or the memory 22 m as reference data. FIG. 7 conceptually shows a portion of the map  1 . According to the map  1 , if the estimated mass of the material  16  is less than or equal to S 1 , the operation mode  1  (corresponding to mass  1 ) is to be performed. If the estimated mass of the material  16  is greater than S 1  and less than or equal to S 2 , the operation mode  2  (correspondingly to mass  2 ) is to be performed. If the estimated mass of the material  16  is greater than S 2  and less than or equal to S 3 , the operation mode  3  (corresponding to mass  3 ) is to be performed. If the estimated mass of the material  16  is greater than S 3  and less than or equal to S 4 , the operation mode  4  (corresponding to mass  4 ) is to be performed. The relationship between quantities S 1 , S 2 , S 3 , and S 4  is: S 1 &lt;S 2 &lt;S 3 &lt;S 4 . 
     FIG. 8 conceptually shows a part of the map  2 . According to the map  2 , in the operation mode  1 , the embroidery data are determined as follows: If a moving distance of the embroidering frame per unit time is one millimeter, a first embroidery data determines that the revolution number of the top shaft  12  is W 11 , and the moving velocity of the embroidering frame is T 11 . If the moving distance of the embroidering frame per unit time is two millimeters, a second embroidery data determines that the revolution number of the top shaft  12  is W 12 , and the moving velocity of the embroidering frame is T 12 . If the moving distance of the embroidering frame per unit time is three millimeters, a third embroidery data determines that the revolution number of the top shaft  12  is W 13 , and the moving velocity of the embroidering frame is T 13 . In the same way, in the operation mode  2 , the embroidery data are determined as follows: If the moving distance of the embroidering frame per unit time is one millimeter, a fourth embroidery data determines that the revolution number of the top shaft  12  is W 21 , and the moving velocity of the embroidering frame is T 21 . The rest of the explanation is omitted. 
     According to the embroidery data shown in FIGS. 7 and 8, if the mass of the material  16  is estimated to be small, the inertia of the material  16  is estimated to be small, and the electric motor (one of the X motor and the Y motor) is controlled such that the electric motor can be driven with larger acceleration and deceleration. If the mass of the material  16  is estimated to be large, the inertia of the material  16  is estimated to be large, and the electric motor (one of the X motor and the Y motor) is controlled such that the electric motor can be driven with smaller acceleration and deceleration. Based on the above control method, the embroidery sewing machine can sew more rapidly and accurately. 
     When the mass of the material  16  is estimated to be small, then the material  16  is rapidly moved to a targeted point by driving the electric motor with increased acceleration Va and deceleration Vd as shown in FIGS.  9 (A) and (B). When the mass of the material  16  is estimated to be large, then the material  16  is slowly moved to the targeted point by driving the electric motor with decreased acceleration Va and deceleration Vd as shown in FIGS.  10 (A) and (B). 
     FIG. 11 shows a flow chart diagram of a control process executed by the main CPU of the embroidering command operator  22 . The embroidering command operator  22  determines whether the needle bar  11  is located at the upper dead point side or not, and determines whether to start the embroidering operation or not in Step.  2  in FIG.  11 . If the embroidering command operator  22  can start the embroidering operation, the embroidering command operator  22  passes to Step.  4 , and then the initial motion command signal A 1  (in FIG.  3 (A)) is sent to the X motor  18  via the X driver circuit  42 . Thus, the material  16  is initially moved in the X-axis direction. Even the frame holder  17  holding the material  16  can be initially moved in Step.  4 . The embroidering command operator  22  passes to Step.  6  and receives the measurement signal Mx thereby passing to Step.  8 . The embroidering command operator  22  measures the measured motor position Sm and calculates the mass of the material. The embroidering command operator  22  further calculates the deviation ΔSa. The deviation ΔSa is the difference between the measured motor position Sm and the standard motor position S 0  previously stored in the memory 22 m. Thus, the embroidering command operator  22  finds the estimated mass of the material  16  by a calculation based on the predetermined formula depending on the deviation ΔSa in Step.  8 . The embroidering command operator  22  send signals for determining the control mode corresponding to the mass of the material  16  to the motors  18  and  19 . The embroidering command operator  22  determines the rotation amount of the top shaft motor  14  corresponding to the above control mode in Step.  12 . The embroidering command operator  22  determines both the moving distance per unit of time of the X motor  18  and the moving distance per unit time of the Y motor  19  suitable to the mass of the material  16  in Step.  14 . Thus, conditions for moving the material  16  and for driving the top shaft  12 , which are adjustable to the variety of the mass of the material  16 , are determined in Step.  14 . The embroidering command operator  22  starts a one stitch embroidering in Step.  16 . The embroidering command operator  22  determines whether the one stitch embroidering is finished or not in Step.  18 . If the one stitch embroidering is finished, then the embroidering command operator  22  determines whether to allow a next one stitch embroidering to start or not in Step.  20 . If the next one stitch embroidering is allowed to start, the embroidering command operator  22  returns to Step.  12 . If not, the embroidering command operator  22  determines whether to stop the next one stitch embroidering or not in Step.  30 . If the next one stitch embroidering is stopped, the embroidering command operator  22  returns to Step.  2 . 
     The triangular pulse as shown in FIG.  3 (A) is used as the initial motion command signal A 1  for initially moving the material  16  in this embodiment. However, even the rectangular pulse as shown in FIG.  3 (B) instead of the above triangular pulse can be used as the initial travel command signal A 2  for driving the X motor  18 . In FIG.  3 (B), the horizontal axis represents time, the vertical axis represents an electric voltage or current charged to the X motor  18 . The initial travel command signal A 2  comprises a first pulse which rapidly increases depending on time and which has a stepped shape and a second pulse which rapidly falls. FIG.  4 (B) shows a characteristic pulse C 2  and a standard characteristic pulse B 2 . The characteristic pulse C 2  is the pulse output by the X motor when the mass of the material  16 , which is not equal to the standard mass, is moved by the X motor  18  upon receiving the initial motion command signal A 2 . The standard characteristic pulse B 2  is the pulse output by the X motor when the mass of the material  16 , which is equal to the standard mass is moved by the X motor  18  upon receiving the initial motion command signal A 2 . As shown in FIG.  4 (B), the characteristic pulse C 2  differs from the standard characteristic pulse B 2 . 
     In this embodiment, prior to embroidering, the mass of the material  16  is estimated. It is also allowable to estimate the mass of the material  16  during the initial stage of the embroidering operation. The material  16  weight is automatically estimated by estimating the mass of the material  16 . Only if the material mass estimation is executed in a short period of time, the material mass estimation during the initial stage of the embroidering operation slightly affects an accuracy of the whole embroidering process. 
     In this embodiment, the material mass estimation is executed by driving the X motor  18  so as to initially move the material  16  in the X-axis direction. It is also allowable for the material mass estimation to be executed by driving the Y motor  19  so as to initially move the material  16  in the Y-axis direction. It is even allowable for the material mass estimation to be executed by driving both the X motor  18  and the Y motor  19 . The estimated material of this invention includes the embroidering frame mass. However, if the embroidering frame mass is precisely known, then it is allowable to estimate only the mass of the material  16  not including the embroidering frame mass. The material mass estimation is applied only to the embroidery sewing machine in this embodiment. However, the material mass estimation can be applied to any type of sewing machine in general use for improving its sewing accuracy. 
     The invention has thus been shown and described with reference to a specific embodiment: However, it should be understood that the invention is in no way limited to the details of the illustrated structures but changes and modifications may be made without departing from the spirit and scope of the appended claims.