WO2002056455A1 - Phase commutation method of four-phase step motor and a device for its realization - Google Patents

Abstract

The invention refers to automatics and electrotechnics and can be used for bipolar control of four-phase step motor acting in the electrical drives of the executive mechanisms of robots, machine tool control systems and computer peripherals. The purpose of the invention is broadening of functional possibilities and spheres of implementation through ensuring 12-, 6-, 4- and 3-tact modes of phase, as well as increase in accuracy, smoothness and uniformity of its rotation. One of the significant peculiarities of the proposed method and the device is that within all phase commutation modes, the positions of torque vectors do not coincide with the poles of the four-phase step motor. This allows to avoid the possible influence of non-linearities of the motor magnet system (e.g. influence of saturation) and, thus, increase to a higher extent the accuracy of adjustment of single steps.

Description

Phase Commutation Method of Four-Phase Step Motor and a Device for Its Realization

This invention refers to automatics and electrotechnics and can be used for bipolar control of four-phase step motor with active and hybrid rotors acting in the electrical drives of the executive mechanisms of robots, machine tool control systems and computer peripherals.

Methods of phase commutation of four-phase step motor [1 ,2] are known which ensure four-tact and eight-tact modes of phase commutation.

The above mentioned methods are imperfect because of unipolarity of phase commutation control and uniformity of distribution on field of absolute values of resulting vectors and their rotation angles.

The closest to the presented one in terms of technical essence is the phase commutation method of four-phase step motor [3], that includes bipolar phase feed and tact step-by-step change of control voltages on the phases.

The imperfections of this method is the limited number of phase commutation tacts (T=4;8) and limited functional possibilities and application spheres, connected to it, as well as low precision of steps adjustment, unsmoothness and ununiformity of motor movement, connected to uneven distribution on field of the absolute value and rotation angles of the vector of motor resulting torque.

The purpose of the presented invention is broadening of functional possibilities and application spheres of phase commutation method of four-phase step motor through ensuring 12-, 6-, 4- and 3-tact phase commutation modes, as well as increase in accuracy, uniformity and smoothness of its rotation by increasing distribution uniformity on the module field and rotation angles of the vector of the motor resulting torque.

The set goal is achieved in the way that by phase commutation method of four-phase step motor, that includes bipolar phase feed and step-by-step tact change of the control voltages on the phases, for ensuring 12-tact phase commutation mode, its each phase is fed within four tact with nominal voltage of positive polarity +Un, within one tact decrease step- by-step voltage to the level of +1/2Un, within one tact switch off the feeding, change the polarity of the feeding voltage to negative and within one tact decrease it step-by-step to the level of -1/2Un, keep under negative nominal voltage of -Un within the following two tact, then within one tact increase step-by-step the voltage to the level of -1/2Un, within one tact switch off the voltage, then change once more the feeding voltage polarity to positive and within one tact increase it step-by-step to the level +1/2Un, at the same time shift the feeding voltages on the phases towards one another for a quarter of a period, for ensuring six-tact phase commutation mode of the motor within one tact feed the first and fourth phases with nominal voltage of positive polarity +Un, and feed the second and third phases with the voltage of negative polarity -1/2Un, within one tact keep on the first phase nominal voltage of positive polarity +Un, on the second phase step-by-step increase the voltage to the level +1/2Un, on the third phase step-by-step decrease the voltage to nominal value of negative polarity — Un, and in the fourth phase switch off the voltage, within one tact on the first phase step-by-step decrease the voltage to level +1/2Un, and on the second phase step-by-step increase the voltage to nominal value of positive polarity +Un, switch off the voltage on the third phase, and on the fourth phase step-by-step decrease the voltage to nominal value of negative polarity — Un, within one tact on the first phase step-by-step decrease the voltage to the level of -1/2Un, on the second phase keep the nominal voltage of positive polarity +Un, on the third phase step-by-step increase the voltage to nominal value of positive polarity +Un, and on the fourth phase step-by-step increase the voltage to the level -1/2Un, within one tact on the first phase step-by-step decrease the voltage to nominal value of negative polarity -Un, switch off the voltage on the second phase, on the third phase keep the nominal voltage of positive polarity +Un, and on the fourth phase step-by-step increase the voltage to +1/2Un, within one tact switch off the voltage on the first phase, on the second phase step-by-step decrease the voltage to nominal value of negative polarity -Un, on the third phase step-by- step decrease the voltage to level +1/2Un, and on the fourth phase step-by-step increase the voltage to nominal value of positive polarity +Un, for ensuring four-tact mode of phase commutation within two tact we feed its each phase with nominal voltage of positive polarity +Un, after which change its polarity to negative and within two tact step-by-step decrease the voltage to the level of -1/2Un, at the same time shift the feeding voltages on the phases towards on another for a quarter of a period, for ensuring of three-tact phase commutation mode of motor within one tact feed its first and fourth phases with nominal voltage of positive polarity +Un, and feed the second and third phases with voltage of negative polarity -1/2Un, within one tact on the first phase step-by-step decrease the voltage to the level of +1/2Un, on the second phase step-by-step increase the voltage to nominal value of positive polarity +Un, switch off the voltage on the third phase, and on the fourth phase step-by-step decrease the voltage to the nominal value of negative polarity -Un, after which within one tact on the first phase step-by-step decrease the voltage to the nominal value of negative polarity -Un, switch off the voltage on the second phase, on the third phase step-by-step increase the voltage to the nominal value of positive polarity +Un, and on the fourth phase step-by-step increase the voltage to the level of +1/2Un. Figures 1 ;3;5;7 present the timing sheets of the control voltages on the phases, and figures 2;4;6;8 present corresponding nomograms of the vector resulting torque for the cases of 12-, 6-, 4- and 3-tact modes for the presented phase commutation mode of the four-phase step motor.

The proposed phase commutation method of four-phase step motor is as follows.

For 12-tact phase commutation mode (fig.1) each phase of four phase step motor is fed with the nominal positive polarity voltage +Un within the first four tact. In the fifth tact the voltage is decreased step-by-step to the level of +1/2Un. The feeding voltage is switched off in the sixth and fourth tact. Then the feeding voltage polarity is changed to negative within the seventh tact and it is step-by-step decreased to the level of -1/2Un. Within the eighth and ninth tact it is kept under negative nominal voltage of -Un. In the tenth tact the voltage is increased to the level of -1/2Un. The voltage is switched off in the eleventh tact. In the last twelfth tact the feeding voltage polarity is changed once more to positive and step-by-step increased to the level +1/2Un. At the same time the feeding voltages on the phases are shifted towards one another for a quarter of a period. In the result of such by-tact distribution of control voltages on phases a 12-angle nomogram of resulting torque of four-phase step motor is developed (fig.2), with high uniformity of distribution on the field and rotation angles (a=30 degrees) of the absolute values of their vectors.

For six-tact phase commutation mode (fig.3) of four-phase step motor within the first tact its first and fourth phases are fed with nominal positive polarity voltage of +Un, and the second and third phases are fed with. the negative polarity voltage -1/2Un. In the second tact on the first phase keep nominal voltage of positive polarity +Un, in the second phase step-by- step increase the voltage to the level of +1/Un, in the third phase step-by-step decrease the voltage to the nominal value of negative polarity -Un, in the fourth phase switch off the voltage. In the third tact on the first phase step-by-step decrease the voltage to level of +1/2Un, in the second phase step-by-step increase the voltage to the nominal value of positive polarity +Un, in the third phase the voltage is switched off, and in the fourth phase step-by-step decrease the voltage to the nominal value of negative polarity -Un. In the fourth tact on the first phase the voltage is step-by-step decreased to the level of -1/2Un, on the second phase nominal voltage of positive polarity +Un is kept, on the third phase step-by- step increase the voltage to nominal value of positive polarity +Un, and in the fourth phase step-by-step increase the voltage to the level of -1/2Un. In the fifth tact on the first phase the voltage is decreased step-by-step to nominal value of negative polarity -Un, on the second phase the voltage is switched off, on the third phase nominal voltage of positive polarity +Un is kept, and on the fourth phase voltage is step-by-step increased to the level +1/2Un. Within the last sixth tact on the first phase the voltage is switched off, on the second phase the voltage is step-by-step decreased to nominal value of negative polarity -Un, on the third phase the voltage is step-by-step decreased to the level +1/2Un, and on the fourth phase the voltage is step-by-step increased to nominal value of positive polarity +Un. In the result of such distribution by tacts of control voltages on the phases a 6-angle nomogram of the resulting torque of four-phase step motor is developed (fig.4), also with a high level of smoothness of distribution on the field and rotation angles (a=60 degrees) of the absolute values of their vectors.

In case of four-tact phase commutation mode (fig.5) of four-phase step motor in the first and second tact its^' each phase is fed wjth nominal voltage of positive polarity +Un. Then change its polarity to negative and within the third and fourth tact step-by-step decrease the voltage to the level -1/2Un. At the same time shift the feeding voltages on the phases towards one another by a quarter of a period. In the result of such distribution by tact of control voltages on the phases a quadrangle nomogram of the resulting torque of four-phase step motor is developed (fig.6), also with a high level of smoothness of distribution on the field and rotation angles (a=90 degrees) of the absolute values of their vectors.

In case of three-tact phase commutation mode (fig.7) of four-phase step-motor in the first tact its first and fourth phases are fed with nominal voltage of positive polarity +Un, and the second and fourth phases are fed with the voltage of negative polarity -1/2Un. In the second tact on the first phase step-by-step decrease the voltage to the level +1/2Un, on the second phase step-by-step increase the voltage to nominal value of positive polarity +Un, on the third phase the voltage is switched off, and on the fourth phase step-by-step decrease the voltage to nominal value of negative polarity -Un. In the last third tact on the first phase step- by-step decrease the voltage to nominal value of negative polarity -Un, in the second phase the voltage is switched off, in the third phase step-by-step increase the voltage to nominal value of positive polarity +Un, and in the fourth phase step-by-step increase the voltage to the level +1/2Un. In the result of such distribution by tact of control voltages on the phases a triangle nomogram of the resulting torque of four-phase step motor is developed (fig.8), also with a high level of uniformity of distribution on the field and rotation angles (a=120 degrees) of the absolute values of their vectors.

Utilization of the proposed phase commutation mode of four-phase step motor with multiple change of phase commutation tact-ness (T=12;6;4;3) allows to vary the value of the single motor step in a wide range (30, 60, 90, 120 degrees), and thus, broaden its functional possibilities and sphere of implementation. High levels of distribution uniformity on the field of the absolute vector values of the resulting torque at that, and their rotation angles highly increase the accuracy of work of single steps, uniformity and smoothness of motor motion. Besides, the proposed method is very simple for utilization and realization, because only two discrete levels of voltages (1/2Uon and Uon) are used for its development.

One of the significant peculiarities of the proposed method, as you can see in nomogarms of the resulting torque vectors on fig. 2;4;6;8, is that within all phase commutation modes the positions of torque vectors do not coincide with the poles of the four- phase step motor. This allows to avoid possible influence of non-linearities of the motor magnet system (e.g. influence of saturation) and, thus, increase to a higher extent the accuracy of adjustment of single steps.

Another important peculiarity of the proposed method can be considered the fact that for its utilization for the control of four-phase step motor single angles of vector moment rotation are adjusted, which are peculiar to three-phase (a=30,60,120 degrees) and six- phase (a=30,60 degrees) step motors. This peculiarity still more broadens the functional possibilities and sphere of utilization of the proposed method.

For realization of the proposed method a device is known for phase commutation of four-phase step motor [4], that contains impulse distributor, power amplifiers, elements OR, current sensors, voltage governors, impulse shapers, blocking unit, amplifiers of feedback, transformers code-analogue.

This device is imperfect because of it is complicated and not reliable.

The closest in terms of technical essence to the presented device for realization of the method of phase commutation of four-phase step motor is the device [5], containing a reversible impulse distributor, four bridge power amplifiers, to the diagonal of which phase windings of motor are connected, and groups of analogue keys. It contains also a counter and a code-analogue transformer.

This device is imperfect because of its complexity and unreliability, low accuracy and non-uniformity of step adjustment.

The purpose of the proposed invention is simplification of the device scheme, increase of reliability, accuracy and uniformity of the motor movement.

The set goal is achieved in the way that it additionally contains a source of reference voltage and resistive voltage divider connected to it, realized on R+R resistors and eight groups of analogue keys, outputs of which are connected to the outputs of respective bridge power amplifiers, signal inputs are connected to the outputs of the resistive voltage divider, and the control inputs - to the outputs canals of the distributor, realized in T-canal, where T is the given tact number of phase commutation of the motor.

Functional layout of the proposed device for phase commutation of four-phase step motor, realizing the proposed method, is presented on fig.9. The device for realization of the proposed method for phase commutation of four- phase step motor contains (fig.9) four bridge power amplifiers 1-4, in the diagonals of which are connected respective phase windings A,B,C,D of motor, reference voltage source Uon 5, resistive voltage divider 6, realized on R+R resistors, eight groups of analogue keys 7-14, signal inputs of which are connected to the respective outputs of voltage divider 6, and the outputs are connected to the inputs of corresponding power amplifiers 1-4, and reversible impulse distributor 15, the outputs of which are connected to control inputs of analogue keys of respective groups 7-14. The number of keys in each group is 7-14 and order of connection of their signal inputs to the outputs of voltage divider 6, as well as the number of output canals of distributor 15 and order of their connection to control inputs of keys 7-14 are selected in accordance with the set tact-ness T(12; 6; 4; 3) of phase commutation of four- phase step motor by the proposed method.

The proposed device works in the following way (fig.9).

Before creation of each of possible phase commutation modes of four-phase step motor, distributor 15 on input R is set in initial position, during which the "1"st logical potential is set on its first output, and on all other outputs "0" logical potentials are set. Depending on the needed direction of rotation of step motor towards its DIR input "1 "st or "0" logical potential is applied. According to proceeding of tact impulses towards C input of distributor 15 alternating shifts of its output canals in one or another direction take place. In the result of this respective shifts of analogue keys 7-14 take place and respective stepped control voltages (fig. 1 ;3;5;7) proceed to inputs of power amplifiers 1-4 from voltage divider 6, which, after amplification, lead to respective rotation of the motor resulting torque vector (fig.2;4;6;8) and adjustment of respective single steps.

Reverse orders of phase shift of step motor are ensured the same way in direct order. Reversing is realized through change of switch directions of output canals of the divider, through change of logical potential to reverse on its DIR input.

Thus, the proposed device is rather simple compared to the analogous known devices and can ensure high reliability.

Information Sources

1. B.π. Py6u,OB, M.C. 3aHAHH n E.A. rieτpHKHH. A.C.CCCP 514410, B.H.18, 1976r.

2. B.π. Py6ιτ,θB, fO.M. Kyp3aHOB, Λ.A. CaAOBCKHH, B.A. HBO6OTΘHKO H 3.C. roHHaπiBHΛH. A.C.CCCP 600682, B.H.12, 1978r. 3. A^HCKP^eτH:bIκ 3ΛeκτpoπpHBθA c raaroBBiMH ABHraTθΛHMH. ΠO pe - MI. HHΛHKHHa. M. SHeprHfl. 1971, cτp.81 (prototype of the method).

4. B.E. AΛUKPHHCKHH, B.Π. PyδiiOB, B.r. MacΛHKOB H H.H. BencraHT. YCTPOHCTBO A » yπpaBΛeHHa m-φa3HHM πiaroBtiM ABHraTeΛeM. A.C.CCCP 738091, B.H.20, 1980r.

5. r.B. ΦpoΛOB, B.r. πoKHAfciπieB, B.M. KaMaeB H T.H. HBaHOBCKHH. YCTPOHCTBO ΛΛH yπpaBΛeHHa πiaroBtiM BHraTeΛeM. A.C.CCCP 1356174, B.H.44, 1987r. (prototype of the device)

Claims

Claims

1. Phase commutation method of four-phase step motor including bipolar phase feeding and tact step-by-step shift of control voltages on the phases, wherein for ensuring twelve-tact phase commutation mode within four tact its each phase is fed with nominal voltage of positive polarity +Un, within one tact step-by-step decrease the voltage to the level of +1/2Un, switch off feeding voltage within one tact, change the polarity of the feeding voltage to negative and within one tact decrease it step-by-step to the level -1/2Un, keep it under negative nominal voltage -Un within the following two tact, then within one tact step-by-step increase the voltage to the level -1/2Un, switch off the feeding voltage within one tact, then once more change the polarity of feeding voltage to positive and within one tact step-by-step increase it to the level +1/2Un, at the same time shift the feeding voltages on the phases towards each other by a quarter of a period, for ensuring six-tact phase commutation mode, within one tact its first and fourth phases are fed with nominal voltage of positive polarity +Un, and the second and third phases - with negative polarity voltage -1/2Un, within one tact keep the nominal voltage of positive polarity +Un, on the second phase step-by-step increase the voltage to the level +1/2Un, on the third phase step-by-step decrease the voltage to nominal value of negative polarity -Un, and on the fourth phase switch off the voltage, within one tact step-by-step decrease the voltage to the level +1/2Un, on the second phase step-by- step increase the voltage to nominal value of positive polarity +Un, on the third phase switch off the voltage, on the fourth phase step-by-step decrease the voltage to nominal value of negative polarity -Un, within one tact on the first phase step-by-step decrease the voltage to the level -1/2Un, on the second phase keep the nominal voltage of positive polarity +Un, on the third phase step-by-step increase the voltage to nominal value of positive polarity +Un, and on the fourth phase step-by-step increase the voltage to the level -1/2Un, within one tact on the first phase step-by-step decrease the voltage to nominal value of negative polarity - Un, on the second phase the voltage is switched off, and on the third phase keep nominal voltage of positive polarity +Un, and on the fourth phase step-by-step increase the voltage to the level +1/2Un, within one tact switch off the voltage, on the second phase step-by-step decrease the voltage to nominal value of negative polarity -Un, on the third phase step-by- step decrease the voltage to the level +1/2Un, and on the fourth phase step-by-step increase the voltage to nominal value of positive polarity +Un, for ensuring four-tact phase commutation mode of the motor its each phase feed with nominal voltage of positive polarity +Un within two tact, after which change its polarity to negative and within two tact step-by- step decrease the- voltage to the level -1/2Un, at the same time shift feeding voltages on the phases towards each other by a quarter of a period, for ensuring three-tact phase commutation mode within one tact feed its first and fourth phases with nominal voltage of positive polarity +Un, the second and third phases - with negative polarity voltage -1/2Un, within one tact on the first phase step-by-step decrease the voltage to the level +1/2Un, on the second phase step-by-step increase the voltage to nominal value of positive polarity +Un, on the third phase switch off the voltage, and on the fourth phase step-by-step decrease the voltage to nominal value of negative polarity -Un, after which within one tact on the first phase step-by-step decrease the voltage to nominal value of negative polarity -Un, on the second phase switch off the voltage, on the third phase step-by-step increase the voltage to nominal value of positive polarity +Un, and on the fourth phase step-by-step increase the voltage to the level +1/2Un.

2. The device for phase commutation of four-phase step motor, realizing the method presented under p.1 , containing a reversible impulse distributor, four bridge power amplifiers, to the diagonals of which respective phase windings of the motor are connected, and groups of analogue keys, wherein the sense that it additionally contains a source of reference voltage and resistive voltage divider, connected to it, worked out on resistors R+R, and eight groups of analogue keys, the outputs of which are connected to the outputs of respective bridge power amplifiers, signal inputs are connected to the outputs of resistive voltage divider, and control inputs - to the output canals of the divider, worked out T-canal, where T is the set number of tact of phase commutation of the motor.