EGIS motor

[dreambox1959]

I have only had German speaking hobbyists answer me about EGIS!
Only 3 people, one of whom owns 3 EGIS !!!
where are the EGIS engine owners ????

 

[7mdish]

I had 3 EGIS motors in my life.
Bought the first in 1989, it was one of the earliest version branded Nitec but including 220 volt power supply instead of 110 volt as in the original one.
The second was 7000 version, the third was 8000 version, both branded EGIS including the additional board with receiver and AGC connectors on the back panel.
So I know that product but not so deeply, it depends what you need.

 

[dreambox1959]

are these 3 devices still in use?
if yes, are they dish prime focus ?
can we have some pictures ?

 

[7mdish]

No, I sold the first two many years ago, the latest was totally destroyed during a tremendous storm last year.
They were all prime focus version. I believe that an offset version is available from EGIS now, but it is very expensive and I'm not sure it is so strong like prime focus one.

 

[dreambox1959]

if you kept the wreck of the egis engine i would be interested in an engine with its gearbox (az or el)

 

[7mdish]

Just trashed. Sorry.

 

[dreambox1959]

I worked on my EGIS engine program (without epr103 but with an equivalent model)
I have some uncertainties on some points:
-How fast can we go down without the motor refusing to move?
-I would like to know if it is necessary to impose a value to the position counter when the origin is found?
-I would like someone with an Egis motor to check the pulse duration.

 

[Hugocz]

Do you already have a response to the above questions?
I might look at my older attempts with PWM. But they will only be the shift values written into the control program. Not a measurement on the engine. Egis was unloaded during these tests.

 

[dreambox1959]

I don't know what is the minimum percentage of PWM cycle with the engine lent by TRUST I went down to 20% but with no load with this value the real speed was still at 40-50%.
I have designed my software so that it can manage 500µs pulses although I have not seen less 800µs pulses (idle).
I am trying to buy an Egis engine but the price of transport makes me hesitate.

 

[dreambox1959]

2 guys have received or will receive a "JPC-POSI" EGIS version.
I too will have an EPR103 soon.
if you are interested, contact me in pm.

 

[dafydd]

Please forgive me for poking my nose into this thread, but as someone who was involved in the design of large servo positioning systems (many years ago, in a previous century!), I have been following it with interest.
It appears that you are close to an ideal solution. Reducing the motor drive voltage proportional to the error (distance from final position) is the correct way to go, as you have done.
Are you using velocity feedback to overcome inertia? A signal derived from your pulse rate and used to reduce motor drive? This may permit you to raise the minimum drive voltage to avoid motor stalling before arriving at your final position. Of course the minimum drive voltage and the amount of velocity feedback would need to be adjusted for each individual installation as there will be variations in the motor characteristics and inertia.

 

[dreambox1959]

I use a mount of my own making (very solid) where the operating clearance is almost non-existent! But above all I have a counterweight which makes that the effort is the same all along the travel.
I wanted to speed up the movements, on my installation I supply the actuator with 48V instead of 36V (a vbox gave 28V) it works since at least 4 years.
But the motor was not stopping fast enough and fine tuning was difficult!
I added a PWM card where I have a progressive acceleration over 2 seconds and a slowdown according to the number of pulses that separate me from the finish.
I added another little thing: I start at a very low fixed speed for 1 second then I accelerate, it allows to optimize the position.
At the deceleration I have no problems, it's only at the start that I must not decrease the speed too much, I have planned to make this parameter adjustable by the user.

 

[dreambox1959]

For the particular case of the EGIS motor the sensor is at the end of the motor shaft, it produces 6 pulses per revolution at 3000 rpm.
At no load the motor turns even faster at 24v and the pulses reach 800nS, the gearing is such that 100 pulses are produced for 1degree (double for me 200 azimuth 400 elevation).
When I switch off the motor supply (at low speed) there are still 15 to 20 pulses produced, so I have set a parameter to stop the motor supply 15 pulses before the end point.
There is one setting per direction and per axis.
In the original controller the value is divided by 10 to be displayed in tenths of a degree, as the error is about 10 points or 0.01 degree it goes unnoticed!

 

[Hugocz]

Unfortunately, I couldn't find the minimum value of the PWM cycle at which the EGIS is still spinning.
During the tests, I solved only the PWM frequency. I tested frequencies in the range of 50 Hz ÷ 500 Hz. EGIS worked on all frequencies. At high frequencies, however, disturbing sounds could be heard from the engine. The subjective impression is that the motor has more power at a frequency of 50Hz and low revolutions.

I'm going to do a new PWM range measurement for the EGIS, but I don't know when I'll get around to it.

 

[Hugocz]

I ran tests on the EGIS engine. The minimum PWM cycle is dependent on the PWM frequency. The minimum frequency of 10 Hz is practically unusable. The engine was no longer running smoothly. The table shows the PWM frequency [ Hz ] / minimum PWM cycle when the EGIS was still moving [ % ].
10/10
50/10
100/15
200/15
300/17
500/20
PWM = 50Hz seems to be the optimal value for minimum smooth motor operation. EGIS was without mechanical load.
The question is whether it would be appropriate to increase the PWM frequency at larger alternating values.

 

[dreambox1959]

i m waiting for my EPR103 (2 weeks) .
i will work on PWM with the egis motor .
actually for classic actuators PWM is running at 5000hz from 10% to 60% above 60% motor runs at full speed .

 

[Hugocz]

I am looking for info on the correct frequency for PWM. It seems to be a complex problem. It should probably be done like this:
1) First, send a pulse to the motor of such length that the motor rotor moves.
2) At low revolutions, maintain this pulse width, regulate revolutions by increasing the frequency. Frequency range from initial about 10Hz to final maximum 2kHz depending on motor coil inductance.
3) Continue to control the revolutions by changing the PWM duty cycle at a constant frequency - greater engine power.

It looks like long experiments or a quick compromise. :-)

AB-022: PWM Frequency For Linear Motion Control - Precision Microdrives

This explains why driving DC motors with PWM works and how it enables control of the current in the windings and in turn the output torque

www.precisionmicrodrives.com

 

[dreambox1959]

after a period of mourning I went back to working on the EGIS engine. I bought a second-hand EGIS set from TRUST, unfortunately the azimuth motor was faulty, there is a circlip inside which had moved, which caused a hell of a noise, and which destroyed the printed circuit of the encoder. the components of the sensor not being found, I replaced by a modern sensor.
it is working now !!
I built an additional positioner in EGIS mode, and I was able to do my first tests, there are still several faults to correct, but that doesn't cause me any problems.

I could reliably verify my program.

 

[Trust]

Nice job
Does this encoder give the same amount of pulses as the original encoder ?

 

[dreambox1959]

Yes !
the original encoder gives 6 pulses per revolution on 2 outputs (it can be used to find the direction) I don't need it, I use only one output.
in the original review they said 100 pulses per degree, if I count each state (top to bottom) I get 200 pulses per degree, so I change my firmware and now I only count the high state, with a single sensor (compatible 5-24V) it is enough.
on the other hand, the defective motor continues to make some noises and electrical parasites!!!!!