CN106788122A - A kind of permanent magnet ac servo system electric current loop bandwidth expanding method - Google Patents

Abstract

The invention discloses a kind of permanent magnet ac servo system electric current loop bandwidth expanding method.According to space vector pulse width modulation principle, the action time of Zero voltage vector is calculated, by the calculating time T for judging microprocessor_calWith the action time threshold value T of zero vector_limRelation, determine current sample and PWM duty cycle update mode：When calculating time T_calLess than or equal to the action time threshold value T of zero vector_limWhen, by the way of immediate updating PWM after current sample calculating；When calculating time T_calMore than the action time threshold value T of zero vector_limWhen, by the way of the sampling of double primary currents updates PWM double times.The present invention reduces current loop time delay in the case where not changing power device switching frequency and not limiting voltage output ability, so as to extend electric current loop bandwidth, improves the control performance of electric current loop.

Description

A kind of permanent magnet ac servo system electric current loop bandwidth expanding method

【Technical field】

The present invention relates to permanent magnetic Ac servo control technology field, especially a kind of permanent magnet ac servo system electric current loop band Extended method wide.

【Background technology】

Permagnetic synchronous motor with its small volume, efficiency high, electromagnetic torque is big, easily safeguard, it is easy to control many advantages, such as, It is widely used to the fields such as Digit Control Machine Tool, Aero-Space, industrial robot.AC servo is general by position ring, speed Ring and electric current loop three control loops composition, wherein, electric current loop as whole system innermost ring, its amount of bandwidth directly affects To speed ring and the response performance of position ring.

In Permanent Magnet AC Servo-Control System, the factor for restricting electric current loop bandwidth mainly includes PWM switching frequencies and control Loop time delay processed.Improving switching frequency can bring the increase of electric current loop bandwidth, but due to by power device performance, being lost and scattered The limitation of heat energy power, the switching frequency general control of middle low power servo-drive system is in 10kHz or so, and room for promotion is little.Therefore, On the premise of keeping PWM switching frequencies constant, reduce the time delay of control loop, to high performance servo system power loop bandwidth Extension is significant.

What conventional electric current loop sequential was typically updated using single current sample single PWM duty cycle in a carrier cycle Mode.In order to improve electric current loop bandwidth, domestic and international many scholars propose the electricity that double PWM duty cycles of double primary current samplings update The electric current loop timing method of stream ring timing strategy and immediate updating PWM duty cycle.Wherein, double update modes of double time sampling can be with By 2~2.67 times of bandwidth expansion to conventional method；Immediate updating mode can be by the 3 of bandwidth expansion to conventional method times of left sides The right side, but the method is realized by appropriate limitation voltage output ability.

【The content of the invention】

To solve problems of the prior art, the present invention provides a kind of permanent magnet ac servo system electric current loop bandwidth and expands Exhibition method, the method can reduce current loop time delay in the case where switching frequency is constant, while also ensuring electricity higher Pressure fan-out capability.

To achieve the above object, the technical solution adopted by the present invention is：

A kind of permanent magnet ac servo system electric current loop bandwidth expanding method, comprises the following steps：

1) define motor and drive phase sequence；

2) judge whether electric current loop response is effective；

3) is carried out by the current sample at t=k moment and PWM duty cycle is calculated for effective electric current loop response, while obtaining forever The calculating time T of the microprocessor of magnetic AC servo_cal；

4) according to space vector pulse width modulation principle, the action time of Zero voltage vector is calculated, by judging microprocessor Calculating time T_calWith the action time threshold value T of zero vector_limRelation, determine current sample and PWM duty cycle update mode： When calculating time T_calLess than or equal to the action time threshold value T of zero vector_limWhen, immediate updating PWM after being calculated using current sample Mode；When calculating time T_calMore than the action time threshold value T of zero vector_limWhen, using double renewal PWM of double primary currents sampling Mode；Update mode carries out the renewal of PWM duty cycle after determining；

5) after PWM duty cycle updates, the electric current loop response at t=k+1 moment, repeat step 2 are carried out)~5).

The action time threshold value T of described zero vector_limMeet：

T_lim=T_0min+T_v

In formula, T_0minIt is the minimum value of zero vector action time；T_vIt is argin, is determined according to actual condition.

The minimum value T of described zero vector action time_0minMeet：

In formula, T_cIt is the triangular carrier cycle；U_refIt is reference voltage vector；U_dcIt is DC bus-bar voltage.

Further, the minimum value T of described zero vector action time_0min, specific calculation procedure is as follows：

Reference voltage vector U_refIn by U₄And U₆In sector between two basic voltage vectors, below equation is obtained：

In formula, T_cIt is the triangular carrier cycle；T₄It is U₄The action time of voltage vector；T₆It is U₆During the effect of voltage vector Between；T_zIt is the effect total time of Zero voltage vector；

In two-phase rest frame α β, each voltage vector and its component have following relation：

θ is U in formula_refAnd U₄Between angle；

Because the modulus value of all of fundamental space vector is 2U_dc/ 3, i.e., | U₄|=| U₆|=2U_dc/ 3, can obtain each The state retention time of vector is：

U in formula_dcIt is DC bus-bar voltage；

Due to two Zero voltage vector v₀And v₇Action time it is identical, respectively account for half, it can thus be concluded that, Zero voltage vector Action time T₀For：

Formula (1) and formula (3) are substituted into formula (4), can be obtained：

In reference voltage vector amplitude | U_ref| it is determined that in the case of, when θ=π/6, the action time of zero vector takes minimum It is worth and is：

When calculating time T_calLess than or equal to the action time threshold value T of zero vector_limWhen, using immediate updating mode, specifically For：Current sample and calculating are carried out in the starting point of each carrier cycle and midpoint, is calculated after new PWM duty cycle, stood Update output.

When calculating time T_calMore than the action time threshold value T of zero vector_limWhen, using double update modes of double samplings, Specially：Current sample and calculating are carried out in the starting point of each carrier cycle and midpoint, is calculated by k instance sample galvanometer PWM duty cycle, output is updated to the k+1 moment again.

Relative to prior art, the present invention has advantages below：

Electric current loop bandwidth expanding method of the invention is by judging the calculating time T of microprocessor_calWith the effect of zero vector Time threshold T_limRelation, determine current sample and PWM duty cycle update mode：When calculating time T_calLess than or equal to zero vector Action time threshold value T_limWhen, by the way of immediate updating PWM after current sample calculating；When calculating time T_calMore than null vector The action time threshold value T of amount_limWhen, by the way of the sampling of double primary currents updates PWM double times.The present invention is constant in switching frequency Under conditions of, reduce the time delay of control loop, electric current loop bandwidth is extended, while ensureing voltage output ability higher, improve electricity Stream ring response performance.

【Brief description of the drawings】

Fig. 1 is electric current loop bandwidth expansion flow chart of the invention；

Fig. 2 is synthesis and the exploded view of reference voltage vector of the invention；

Fig. 3 is immediate updating timing diagram of the invention；

Fig. 4 is that double samplings of the invention update timing diagram double times.

【Specific embodiment】

Further to illustrate the technical solution adopted in the present invention, below in conjunction with accompanying drawing to specific embodiment party of the invention Formula is described in detail.The implementation method is only applicable to the description and interpretation present invention, does not constitute to the scope of the present invention Restriction.

As shown in figure 1, a kind of flow of permanent magnet ac servo system electric current loop bandwidth expanding method of the invention, including with Lower step：

1) define motor and drive phase sequence；

2) judge whether electric current loop response is effective；

3) is carried out by the current sample at t=k moment and PWM duty cycle is calculated for effective electric current loop response, while obtaining forever The calculating time T of the microprocessor of magnetic AC servo_cal；

4) according to space vector pulse width modulation principle, the action time of Zero voltage vector is calculated, by judging microprocessor Calculating time T_calWith the action time threshold value T of zero vector_limRelation, determine current sample and PWM duty cycle update mode： When calculating time T_calLess than or equal to the action time threshold value T of zero vector_limWhen, immediate updating PWM after being calculated using current sample Mode；When calculating time T_calMore than the action time threshold value T of zero vector_limWhen, using double renewal PWM of double primary currents sampling Mode；Update mode carries out the renewal of PWM duty cycle after determining；

5) after PWM duty cycle updates, the electric current loop response at t=k+1 moment, repeat step 2 are carried out)~5).

Specific embodiment is as follows：

As shown in Fig. 2 the synthesis of reference voltage vector and decomposition.In figure, reference voltage vector U_refIn by U₄And U₆ In sector between two basic voltage vectors.Below equation can be obtained：

In formula, T_cIt is the triangular carrier cycle；T₄It is U₄The action time of voltage vector；T₆It is U₆During the effect of voltage vector Between；T_zIt is the effect total time of Zero voltage vector.

In two-phase rest frame α β, each voltage vector and its component have following relation：

θ is U in formula_refAnd U₄Between angle.

Because the modulus value of all of fundamental space vector is 2U_dc/ 3, i.e., | U₄|=| U₆|=2U_dc/ 3, it is possible to State retention time to each vector is：

U in formula_dcIt is DC bus-bar voltage.

Due to two Zero voltage vector v₀And v₇Action time it is identical, respectively account for half, it can thus be concluded that, Zero voltage vector Action time T₀For：

Formula (1) and formula (3) are substituted into formula (4), can be obtained：

As can be seen that in reference voltage vector amplitude | U_ref| it is determined that in the case of, when θ=π/6, the effect of zero vector Time takes minimum value：

According to the characteristics of digital display circuit current loop control sequential, using the calculating time of high speed microprocessor actual operation T_calIf it was determined that it is still Zero voltage vector to calculate PWM outputs when completing, then immediate updating mode can be used, stood Update PWM duty cycle.As the condition for judging, while considering the safety and reliability of control, it is stipulated that the action time of zero vector Threshold value is：

T_lim=T_0min+T_v (7)

T in formula_vIt is argin, can be determined according to actual condition.

When calculating time T_calLess than or equal to the action time threshold value T of zero vector_limWhen, using immediate updating mode, its electricity Stream ring sequential is as shown in Figure 3.In the sequential, current sample and calculating are carried out in the starting point of each carrier cycle and midpoint, calculated Obtain after new PWM duty cycle, output is updated immediately.

When calculating time T_calMore than the action time threshold value T of zero vector_limWhen, using double update modes of double samplings, Its electric current loop sequential is as shown in Figure 4.It is also to carry out current sample and meter in the starting point of each carrier cycle and midpoint in the sequential Calculate, unlike, the PWM duty cycle calculated by k instance sample galvanometer will could update to the k+1 moment.

In sum, a kind of permanent magnet ac servo system electric current loop bandwidth expanding method that the present invention is provided, by judging The calculating time T of microprocessor_calWith the action time threshold value T of zero vector_limRelation, determine current sample and PWM duty cycle Update mode：When calculating time T_calLess than or equal to the action time threshold value T of zero vector_limWhen, using immediate updating mode；Work as meter Evaluation time T_calMore than the action time threshold value T of zero vector_limWhen, using double update modes of double samplings.The present invention is not changing Under conditions of Variable power devices switch frequency, reduce current loop time delay, while ensure voltage output ability higher, extension electricity Stream loop bandwidth, improves electric current loop response performance.

Embodiments of the present invention are explained in detail above in conjunction with accompanying drawing, not the present invention is imposed any restrictions, it is all It is any simple modification, change and the equivalent structure change substantially made to above embodiment according to the technology of the present invention, Still fall within the protection domain of technical solution of the present invention.

Claims (6)

1. a kind of permanent magnet ac servo system electric current loop bandwidth expanding method, it is characterised in that comprise the following steps：

1) define motor and drive phase sequence；

2) judge whether electric current loop response is effective；

3) is carried out by the current sample at t=k moment and PWM duty cycle is calculated for effective electric current loop response, while obtaining permanent magnetism friendship Flow the calculating time T of the microprocessor of servo-drive system_cal；

4) according to space vector pulse width modulation principle, the action time of Zero voltage vector is calculated, by the meter for judging microprocessor Evaluation time T_calWith the action time threshold value T of zero vector_limRelation, determine current sample and PWM duty cycle update mode：Work as meter Evaluation time T_calLess than or equal to the action time threshold value T of zero vector_limWhen, the side of immediate updating PWM after being calculated using current sample Formula；When calculating time T_calMore than the action time threshold value T of zero vector_limWhen, update the side of PWM for double times using the sampling of double primary currents Formula；Update mode carries out the renewal of PWM duty cycle after determining；

5) after PWM duty cycle updates, the electric current loop response at t=k+1 moment, repeat step 2 are carried out)~5).

2. a kind of permanent magnet ac servo system electric current loop bandwidth expanding method according to claim 1, it is characterised in that：Institute The action time threshold value T of the zero vector stated_limMeet：

T_lim=T_0min+T_v

In formula, T_0minIt is the minimum value of zero vector action time；T_vIt is argin, is determined according to actual condition.

3. a kind of permanent magnet ac servo system electric current loop bandwidth expanding method according to claim 2, it is characterised in that：Institute The minimum value T of the zero vector action time stated_0minMeet：

$T_{0\min }=\frac{1}{2}{T}_c\[1-\frac{\sqrt{3}\left|U_{ref}\right|}{U_{dc}}\]$

In formula, T_cIt is the triangular carrier cycle；U_refIt is reference voltage vector；U_dcIt is DC bus-bar voltage.

4. a kind of permanent magnet ac servo system electric current loop bandwidth expanding method according to claim 3, it is characterised in that：Institute The minimum value T of the zero vector action time stated_0min, specific calculation procedure is as follows：

Reference voltage vector U_refIn by U₄And U₆In sector between two basic voltage vectors, below equation is obtained：

$\left\{\begin{array}{c}{T}_c=T_4+T_6+T_z\\ U_{ref}=\frac{T_4}{T_c}{U}_4+\frac{T_6}{T_c}{U}_6\end{array}\right.---\left(1\right)$

In formula, T_cIt is the triangular carrier cycle；T₄It is U₄The action time of voltage vector；T₆It is U₆The action time of voltage vector；T_z It is the effect total time of Zero voltage vector；

In two-phase rest frame α β, each voltage vector and its component have following relation：

$\left\{\begin{array}{c}\left|U_{ref}\right|cos\mathrm{\θ}=\frac{T_4}{T_c}\left|U_4\right|+\frac{T_6}{T_c}\left|U_6\right|cos\frac{\mathrm{\π}}{3}\\ \left|U_{ref}\right|\sin \mathrm{\θ}=\frac{T_6}{T_c}\left|U_6\right|\sin \frac{\mathrm{\π}}{3}\end{array}\right.---\left(2\right)$

θ is U in formula_refAnd U₄Between angle；

Because the modulus value of all of fundamental space vector is 2U_dc/ 3, i.e., | U₄|=| U₆|=2U_dc/ 3, each vector can be obtained State retention time be：

$\{\begin{array}{c}{T}_4=\frac{\sqrt{3}\left|U_{ref}\right|}{U_{dc}}{T}_{c}sin(\frac{\mathrm{\π}}{3}-\mathrm{\θ})\\ T_6=\frac{\sqrt{3}\left|U_{ref}\right|}{U_{dc}}{T}_c\sin \mathrm{\θ}\end{array}---\left(3\right)$

U in formula_dcIt is DC bus-bar voltage；

Due to two Zero voltage vector v₀And v₇Action time it is identical, respectively account for half, it can thus be concluded that, the effect of Zero voltage vector Time T₀For：

$T_0=\frac{1}{2}{T}_z---\left(4\right)$

Formula (1) and formula (3) are substituted into formula (4), can be obtained：

$T_0=\frac{1}{2}{T}_c\[1-\frac{\sqrt{3}\left|U_{ref}\right|}{U_{dc}}cos(\frac{\mathrm{\π}}{6}-\mathrm{\θ})\]---\left(5\right)$

In reference voltage vector amplitude | U_ref| it is determined that in the case of, when θ=π/6, the action time of zero vector takes minimum value For：

$T_{0\min }=\frac{1}{2}{T}_c\[1-\frac{\sqrt{3}\left|U_{ref}\right|}{U_{dc}}\]---\left(6\right).$

5. a kind of permanent magnet ac servo system electric current loop bandwidth expanding method according to claim 1, it is characterised in that：When Calculating time T_calLess than or equal to the action time threshold value T of zero vector_limWhen, using immediate updating mode, specially：In each load The starting point of period of wave and midpoint carry out current sample and calculating, are calculated after new PWM duty cycle, and output is updated immediately.

6. a kind of permanent magnet ac servo system electric current loop bandwidth expanding method according to claim 1, it is characterised in that：When Calculating time T_calMore than the action time threshold value T of zero vector_limWhen, using double update modes of double time samplings, specially：Every The starting point of individual carrier cycle and midpoint carry out current sample and calculating, the PWM duty cycle calculated by k instance sample galvanometer, to k + 1 moment was updated output again.