Hacking an angular position sensor

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rmeldo

Senior Member
Hi forum,

I haven't posted a message for a while, being busy in raising my kid.

At work however we have a small project we are trying to mae sense of and I tought I would ask the forum. I know how people feel about giving advice for business use. I am not asking for any time intensive input, just the best advice people are willing to give.

I am trying to hack into a integrated motor-angular position sensor with onboard control electronics to try and take control of it. This system is used in a car engine.

First of all I want to make clear that I do not intend to use the motor on the engine itself. It will not go in a car or any other safety critical application. I must however try and make use of that specific motor to avoid expensive reworking.

The motor package contains a gearbox with worm gears which convert the rotor rotation into axial displacement of a shaft. An angular position sensor is also integrated into the system.

The reason I want to do this is because the system is impenetrable to me, because the communication of the motor+sensor with the outside is via CAN protocol. I would like to replace the onboard electronics with a suitable motor controller.

I attach the photographs of the magnetic wheel poles and the five sensors.
The sensors are labeled Z10 95E4. A search on google was less than satisfactory.

From the photographs I can see that two of the five sensors are positioned at an outer radius than the other three and that all together they should be capable to resolve the sense of rotation and the angular position. The rotor spins for several revolutions to move the shaft axially.

Can anyone help me understand how these sensors work?
Any suggestions on how to connect them together to achieve the detection of position and sense of rotation?
Does anyone know what those components (Z10 95E4 ) are?

thanks in advance

Riccardo
 

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BeanieBots

Moderator
Welcome back rmeldo.

I'd agree with AC that they look like hall effect sensors but I've not seen that arrangement before.

Do you know the resolution of the existing system?
What resolution do you NEED.

If I was in your position, I'd start probing those 'devices' with a 'scope and see if anything meaningful comes out while the motor rotates. I'd also be looking closely at the internal electronics to see if any of the sensor interfacing chips can be identified.

The bad news is that it does NOT look like a simple quadrature device but I might be wrong. A plot of each devices output in relation to each other would answer many questions.
 
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westaust55

Moderator
From some extremely large motors (15,000kW and around 18m in diameter) I worked with a few years back the motor had a number of sensors (9 in total) used simultaneously for:
1. speed
2. direction
3. airgap monitoring
4. position

the sensors were generally in pairs at quadrature position primarily for airgap measurement. Used as 9 separate sensors at start-up but then switched into two sets and could then run even if one at each position failed.

Speed could be done with any pair.

The position of the 9th sensor was at a half-pole position to better resolve the motor position (motor had from memory around 48 poles on the rotor) and verify direction.

so the cluster of three could be for both direction and half pole position sensing. The three would also enable speed detection but does raise the question why the extra 2 sensors.


Then again, if you are going to design a new controller, does it matter greatly how the sensors are currently used?
Just use what you need for your own application. Maybe even replace the sensors if necessary with something for which you can get a datasheet.
 
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