Show the electromotor position nowadays to send feeling kind varied, optical coder because its pinpoint accuracy and “ABI” of standardization of pilot of Yi Shouwei controller are outputted and the times favour that accepts electric machinery to control systematic architect.

 

But as a result of a variety of reasons, sensor of position of blame contact magnetism made better choice now. Because the size of magnetic position sensor is smaller, can resist the contaminant such as dirt, grease, lunt, consequently can action at be opposite dimension is mixed / the application that may rely on a gender to have higher demand.

 

 

In the past, have an adverse to magnetic position sensor tendency: New-style without brush dc (BLDC) electromotor is in have on the whole efficient target, in order to reduce power comsumption. Meanwhile, the architect was gifted the job that adds moment of force of new electric machinery, the low rotate speed that realizes electric machinery moves, in order to support direct drive system. Final, transmission will be requisite no longer, this reduced stock cost greatly.

 

Should make so that pitching moment and efficiency achieve the biggest change, without brush dc motive to there must be an extremely accurate engine to rotate below high rotate speed angle data —— uses traditional magnetic sensor is very rare. Now, new generation product had achieved the one big breakthrough that sensor designs, they can measure the corner coming back below high rotate speed accurately to spend almost.

 

How to realize angle to measure

 

One is not had brushed dc motive to include motor of a permanent magnetism (rotor) mix 3 or 3 above are equidistant fixed coil (stator) . Through controlling fixed coil medium electric current can form the magnetic field of an aleatoric direction and size. Pitching moment originates the gravitation between the rotor that moves on runner shaft and fixed coil and repulsion.

 

When fixed coil magnetic field and rotor magnetic field are mutual and perpendicular, pitching moment reachs maximum. The system that measures rotor point of view feedbacks to control electric current through securing coil (see a picture 1) , produce a perpendicular magnetic field.

 

Graph 1: One is not had brush dc machine to control a system to need to carry magnetic position sensor (use at car domain normally) or optical position

 

In application of most high end, without brush dc motive to be in by electromotor of permanent magnetism synchronism (PMSM) be replaced. Synchronous electromotor replaced permanent magnetism to not have torsion suffers in brushing dc motive the module commutation plan of pulsatile influence, and can freely between coil switch, reduce vibration, achieve taller efficiency.

 

Of course, although industry and the efficiency that car electromotor designs and dependability often must get optimizing, a lot of other electromotor, especially the electromotor of consumer goods domain still pays attention to cost most. To simple electromotor, array of suddenly Er switch offerred appropriate positional measurement technique, also can produce opportune moment, make the operation becomes fluent.

 

But the accuracy of array of suddenly Er switch and accuracy often high-powered engine is opposite short of the requirement of pitching moment and utilization rate. Contrarily, magnetic coder (sensor of will suddenly Er is compositive a semiconductor in silicon chip) the positional data that can generate pinpoint accuracy, high resolution. It can undertake accurate measurement to the runner shaft below static condition or low rotate speed. With industrial application commonly used optical coder differs, magnetic position sensor won’t get the influence of contaminant, and take up the space is very little.

 

On the other hand, chip of sensor of most suddenly Er has two big drawback: The high rotate speed that transmission defer brings about leaves dynamic angle error; Screen measure needs below environment of stray magnetic field.

 

These blemish can raise systematic cost, weaken systematic performance. Compensation of dynamic angle error needs very strong processing capability, to stray magnetic field medium IC undertakes additional protection also can raise the stock cost of hardware.

 

The origin of dynamic angle error

 

Chip of suddenly Er sensor samples continuously read the magnetic field strength that takes the magnet on runner shaft. Chip is in to secure the position by installation, its surface parallel turns at coming back the surface of magnet, there is the 1 space to 2 millimeters normally between chip and magnet.

 

A signal adjustment and processing return are included in chip, the angle place that will measure the conversion of magnetic field intensity that go out to be rotor (with degree form) . The time that this one changeover needs is the transmission defer that chip secures (see a picture 2) . The time that different chip defer lasts varies, but the chip on current market transmits defer to arrive in 10μs normally between 400μs.

 

Graph 2: The signal processing in magnetic position sensor causes transmission delay

 

The problem of transmission defer caused dynamic angle error when rotor is rotational. Dynamic angle error can show linear growth as speed; Transmission defer and rate are higher, dynamic angle error is bigger. (see a picture 3) .

 

Graph the 3 addition that showed dynamic angle error. Hypothesis chip is read when rotor is in red line position take magnetic field strength, and chip is 100μs in the transmission defer when rotor is rotational. When chip is conversion of magnetic field intensity angle, is rotor used 100? The time of S turns to —— of blue line position but chip still is in to indication rotor of ECU or MCU red line position.

 

Graph 3: The linear between rotate speed of dynamic angle sum of errors concerns

 

Below circumstance of error wanting compensatory, the electric current in adjusting plan can arrive in the starting coil of red line position, is not blue position, the result causes a system cannot pitching moment the biggest change, waste energy thereby, reduce systematic efficiency.

 

If the transmission defer of chip is 100μs, the rotate speed of engine is 1000 turn every second, error of so dynamic angle is 1.2 degrees. If the rotate speed of rotor is added to 10, 000 turn every second, dynamic angle error is added reach 12 degrees.

 

Graph 4: How does transmission defer increase dynamic angle error

 

Transmission defer is the characteristic of all magnetic position sensor, because this system designs an engineer,try to will compensate algorithmic at reducing dynamic angle error applying. Unfortunate is, the compensation of example of thousands of data meets every second create serious burden to lead plane ECU, need even additional and custom-built MCU of appropriative of an error compensation.

 

Design group does not hope from raise stock cost substantially, also do not want to cost too much time to come development, test and the compensation that amend them are algorithmic.

 

New-style sensor reduces dynamic angle error

 

If what a moment ago said, the transmission defer of magnetic position sensor is fixed, and the value of dynamic angle error depends on the time of transmission defer and rotate speed.

 

Now, austrian microelectronics has developed new compensation plan to apply in magnetic sensor, this plan is in patent application. This kind of new in-house compensation technology is called DAEC (dynamic angle error is compensated) , try the magnetic sensor that is used at 47 series above all. The transmission defer error that DAEC can reduce AS5147 of car seat sensor effectively comes only 1.9μs. This means AS5147 to be in 14, 500 turn below the rotate speed of every second, dynamic angle error is 0.17 degrees only, almost negligible not plan.

 

Graph 5: The sensor of compositive compensation program is outputted (left) and the sensor of program of not compositive compensation is outputted (right)

 

Graph 6 showed AS5147 (left) sensor of as magnetic as the tradition position (right) the distinction that measures output, accurate optical coder output serves as reference. Right graph shows sensor output is transmitted the influence of defer by 200μs, in 14, 500 turn the dynamic angle error of the generation below the rotate speed of every second is 18 degrees.

 

Graph 6: The compensation method of error of angle of dispersive type trends that Zun Tu demonstrated a tradition. Right graph demonstrated compensation method of new dynamic angle error.

 

Contrary, the error of AS5147 is almost negligible not plan, that is to say its signal can be used at adjusting controller directly, need not exterior compensation. In fact, the dynamic angle error that the in-house compensation that contains DAEC technology produces may compare exterior compensation smaller, because ECU and MCU middling regular meeting have error of sampling.

 

Of course, sensor interior compensation still can reduce systematic cost, the reason is to do not have additional MCU, or it is to be able to be used more the ECU of small-power.

 

Resist stray magnetic field

 

Another malpractice of a lot of magnetic sensor is to get easily the interference of stray magnetic field. The magnetic field interference beyond rotor magnet can destroy the angle of chip to measure at any time, and mistake of this kind of random cannot pass lead plane ECU or MCU remedies. Accordingly, the user must take screen step to chip, this added stock cost and assemble cost; Violate the structural design that has requirement application to the space possibly still.

 

According to standard of safety of function of ISO 26262 car, those who avoid the interference that gets stray magnetic field to had made engine system is mandatory requirement.

 

In all magnetic position sensor that “ differs cent to pass feeling ” patent technology to be applied at Austrian microelectronics, include 47 series, make sensor avoids the highest value that gets effect of stray magnetic field to achieve 25, 000A/m. Under this critical value, need not take screen step.

 

Conclusion

 

Of technology of Austrian microelectronics DAEC roll out mean achieve without the torsion in brushing manufacturer of dc motive and electromotor of permanent magnetism synchronism to be able to use extremely accurate position data to make high rotate speed applies the biggest change, narrow through magnetic position sensor at the same time the dimension of electromotor, raise dependability.

 

DAEC technology already applied at circle of AS5147* monolayer brilliant now) with AS5247 (double deck is redundant brilliant is round) sensor of car magnetism position (0 cars use AEC-Q100 level attestation) , support is not had brush the dc motive application in car domain, be like electronic motivation steering wheel (EPS) , gearing (gear-box, motivate implement) , pump and brake.

 

The field uses in industry, the AS5047D that uses DAEC technology is devoted already also use, offer decimal ABI output, be the ideal that replaces optical coder anthology.