A kind of compensation method of brushless DC motor without position sensor voltage sample offset
Technical field
The present invention relates to a kind of compensation methodes of brushless DC motor without position sensor voltage sample offset, belong to motor
Drive area.
Background technique
Brshless DC motor due to high power density, high efficiency, low-maintenance cost, structure it is simple and easily controllable etc.
Advantage is widely used in various fields, such as household electrical appliance, industrial equipment, unmanned plane and electric car.Brshless DC motor by
Three-phase inverter driving provides six discrete rotor-positions usually using three Hall sensors, controls to three-phase windings
Commutation control processed, and then carry out commutation appropriate.However, rotor-position sensor increases cost and reduces reliability.Cause
This, method for controlling position-less sensor is in the past decade developed.It is controlled in brushless DC motor without position sensor
It mainly include counter electromotive force method, freewheeling diode method and flux linkage estimation method etc. in method.Wherein counter electromotive force method is passed without position
Sensor brshless DC motor is most widely used.The counter electromotive force of brshless DC motor can not be measured directly, usually utilize electricity
Perhaps then line voltage difference signal is filtered out in line voltage difference or phase voltage the phase voltage of pressure sensor sample motor with filter
High-frequency Interference, then detect its zero crossing.But because operation is put in the sensitivity deficiency and filter circuit of voltage sensor
The null offset of big device often makes the line voltage difference of sampling or phase voltage signal generate offset, forms unbalanced zero passage
Point influences the accurate commutation of brshless DC motor, and it is abnormal that serious conditions will cause brshless DC motor runnability.
Summary of the invention
For the above-mentioned prior art, the technical problem to be solved in the present invention is to provide one kind can solve voltage sample offset
The compensation method of the brushless DC motor without position sensor voltage sample offset of the uneven zero crossing of formation.
In order to solve the above technical problems, a kind of benefit of brushless DC motor without position sensor voltage sample offset of the present invention
Compensation method, comprising the following steps:
Step 1: brushless DC motor rotor is pre-positioned, and applies phase change logic to brshless DC motor, dragging motor arrives
Certain revolving speed;
Step 2: detection brushless dc generator terminal voltage or line voltage difference signal, opposite end voltage or line voltage difference signal into
Row filtering, test side voltage or line voltage difference signal zero crossing, form the virtual hall signal T in three tunnelsa、Tb、Tc;
Step 3: hall signal T virtual to three tunnelsa、Tb、TcIt carries out XOR operation and obtains Tpos, wherein TposRising edge and
Failing edge is identical as counter electromotive force dead-center position;
Step 4: T is calculatedposFor high level lasting time tθ1, calculate TposFor the low level duration tθ2;
Step 5: current period t is utilizedθ1、tθ2Calculate the revolving speed of brshless DC motor, revolving speed expression formula are as follows:
Wherein p is the number of pole-pairs of motor;
Step 6: by next period back electromotive force zero-crossing information Ta、Tb、TcLag 0.5tθ1-tθf, form Ta'、Tb'、
Tc'.Lag 0.5tθ2-tθf, form Ta”、Tb”、Tc", wherein tθfLag time caused by filter;
Step 7: S is carried outa=Ta'∩Ta”、Sb=Tb'∩Tb”、Sc=Tc'∩Tc" operation, respectively obtain commutation signal
Sa、Sb、Sc;
Step 8: commutation signal generates the phase change logic of motor, is input to the operation of three-phase fully-controlled inverter circuit driving motor.
The invention has the advantages that: compared with prior art, the present invention considers voltage sensor and operational amplifier circuit to no position
The influence for setting the sampling of sensor brushless DC motor position signal still may be used in voltage sensor under-sensitive
Accurately to correct unbalanced zero crossing, hardware cost is reduced.
Detailed description of the invention
Fig. 1 is brshless DC motor equivalent circuit;
Fig. 2 (a) is voltage sensor line voltage difference sample waveform figure;
Fig. 2 (b) is voltage sensor line voltage difference sample waveform figure;
Fig. 3 is influence of the variation to zero passage point sampling;
Fig. 4 is backoff algorithm system diagram;
Fig. 5 is filter circuit figure;
Fig. 6 is back electromotive force zero-crossing signal and commutation point signal;
Fig. 7 is that delay-angle calculates waveform diagram.
Specific embodiment
The present invention will be further described with reference to the accompanying drawing:
Based on counter electromotive force method, brushless DC motor without position sensor needs to sample during obtaining location information
Phase voltage or line voltage are poor, due to the null offset meeting of operational amplifier in voltage sensor sensitivity deficiency and filter circuit
The line voltage difference or phase voltage signal for making sampling generate offset, form unbalanced zero crossing, influence motor commutation, seriously affect
Motor operation.For this problem, the present invention analyzes variation to mistake according to back electromotive force zero-crossing information during commutation
The influence of zero sample proposes a kind of compensation method of brushless DC motor without position sensor voltage sample offset.It utilizes
The compensation control system that simulation means are realized has carried out corresponding after system-computed goes out error in subsequent commutating period
Compensation, the results showed that the feasibility and validity of this method.
A kind of compensation method of brushless DC motor without position sensor voltage sample offset of the present invention, including brushless direct-current
Motor, three-phase fully-controlled inverter circuit, position detecting module, controller, voltage offset compensation module and filtering compensation module;Position
Detection module using voltage sensor sample motor line voltage difference or phase voltage, and by filter filter out line voltage it is poor or
High-frequency Interference in phase voltage generates phase change logic by detection zero crossing.Filtering compensation module is compensated because of filter bring
Lag angle, controller include speed regulator and current regulator, and voltage offset compensation module is used to compensate because of variation
Caused by unbalanced commutation signal.The following steps are included:
Step 1: brushless DC motor rotor is pre-positioned, and applies phase change logic to brshless DC motor, dragging motor arrives
Certain revolving speed, normally about 300rpm.
Step 2: detection brushless dc generator terminal voltage or line voltage are poor, are filtered, and detect its zero crossing, form three
The virtual hall signal T in roada、Tb、Tc。
Step 3: hall signal T virtual to three tunnelsa、Tb、TcIt carries out XOR operation and obtains Tpos, wherein TposRising edge and
Failing edge is identical as counter electromotive force dead-center position.
Step 4: work as TposWhen=1, high level lasting time t is calculatedθ1, work as TposWhen=0, low level time t is calculatedθ2。
Step 5: current period t is utilizedθ1、tθ2Calculate the revolving speed of brshless DC motor, revolving speed expression formula are as follows:
Wherein p is the number of pole-pairs of motor.
Step 6: by next period back electromotive force zero-crossing information Ta、Tb、TcLag 0.5tθ1-tθf, form Ta'、Tb'、
Tc'.Lag 0.5tθ2-tθf, form Ta”、Tb”、Tc".Wherein tθfLag time caused by filter.
Step 7: S is carried outa=Ta'∩Ta”、Sb=Tb'∩Tb”、Sc=Tc'∩Tc" operation, respectively obtain commutation signal
Sa、Sb、Sc。
Step 8: commutation signal generates the phase change logic of motor, is input to the operation of three-phase fully-controlled inverter circuit driving motor.
The present invention is by taking the sampling of line voltage difference as an example, as shown in Figure 1, brshless DC motor, is connected 120 ° of conduction modes two-by-two
Under, the line voltage eikonal equation of motor is
R in figure, L respectively indicate the resistance and inductance (difference that inductance is self-induction and mutual inductance) of every phase winding.ua、ub、ucFor
Phase voltage, ea、eb、ecFor phase back-emf, ia, ib, icFor phase current.
By ubcWith ucaSubtract each other, obtains
When AC is conducted, B phase is non-conduction phase.There is ia+ib+ic=0, ea+ec=0.Formula (2) is updated to obtain
B phase is used as non-conduction phase, electric current 0.That is 2eb=ubc-uab.Counter electromotive force is only related with line voltage difference.Therefore pass through
The zero crossing of counter electromotive force can be obtained in the zero crossing of sampling line voltage difference.The a certain offline voltage difference sampling of revolving speed in actual measurement
As shown in Fig. 2 (a) and Fig. 2 (b), peak value 3.74V, valley is -3.5V, therefore there is 0.12V variations.
The null offset of operational amplifier in voltage sensor and filter module produces nonequilibrium zero crossing.
Traditional brushless DC motor without position sensor postpones 30 ° of commutations after the zero crossing for sampling counter electromotive force, but according to
This method, the commutation point that nonequilibrium zero crossing generates is also that width is different.Fig. 3 shows balance zero-crossing examination and not
Balance the comparison of zero-crossing examination.By the way that shown in Fig. 3, no matter whether zero crossing is balanced, and commutation point is in the centre of two zero crossings
At position, therefore the compensation method that can use the uneven zero crossing in claims solves to encounter when the sampling of line voltage difference
Non-equilibrium zero crossing the problem of, as shown in figure 4, be claims proposed method system diagram.
Embodiment
In order to verify a kind of compensation of brushless DC motor without position sensor voltage sample offset proposed by the invention
Method validity, the present invention have carried out simulating, verifying.Filtering used of the invention uses second-order low-pass filter, filter circuit impedance ginseng
Several and schematic diagram is as shown in Figure 5.
Using traditional three steps start, any two-phase stator winding electrifying is given for a period of time by control program, stator
Rotor is dragged to specified position by magnetic field, is successively powered according to switch list to winding, is increased to one to brshless DC motor revolving speed
After definite value, it is switched under method for controlling position-less sensor and runs.By the calculation method of revolving speed in claims, calculate current
Revolving speed.And the lag angle caused by filtering is calculated according to circuit filtering parameter, wherein α is system damping coefficient, ω0For system
Intrinsic frequency, ω are angular speed, θf(ω) is phase delay angle, and specific formula for calculation is as follows
Zero passage generates three and passes by zero signal T after the filtering of line voltage differencea、Tb、TcAs shown in fig. 6, according in claims
Method carry out signal processing, commutation delay-angle calculates as shown in Figure 7.What comparison position-sensor-free generated in simulations changes
Phase signals SaThe commutation signal H generated with position sensora, SaWith HaRising edge and failing edge having the same, after correction
The commutation signal of brushless DC motor without position sensor can replace the commutation information of position sensor offer, and accurately change
Phase, therefore a kind of compensation method of brushless DC motor without position sensor voltage sample offset proposed by the invention can solve
Zero crossing energy imbalance caused by variation certainly because sampling and filtering generation.