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Needed for Expansion: Universal Turret Base
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rhoude57 - YUL
Second Officer
Canada
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Looking at expansion capabilities for the RoboMaster S1, I keep coming across the requirement for a minimal turret base on which expansion mechanisms could be mounted. This Universal Base would include:
a chassis interface allowing to mount the turret on the existing 4 mounting holes;
a turret yaw motor with pass-through for mechanism cables and CAN-Bus interface;
  • optionally, a mechanical interface for a slipring;

the CAN-Bus cable connecting to the Interface Module; and
a universal mechanism mounting interface.

What do you think?

2019-12-12
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Napalm78
lvl.1
France
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Hi !

Great idea, had the same on my side to mount lighter form of the current turret.

Never heard of sliprings befire today, you made my day ! I'll look forward to test someting on Catia.

Does anyone know if we can get CAN wiring easily ? 3D-Print connectors is kind of a pain in the ass
2019-12-13
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Napalm78
lvl.1
France
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Another question : with kind of BLDC motor would you use for Yaw axis ?

I'm currently working on hollow shaft BLDC motor mainly used for gimbal. It allows wiring to pass through so you can plug other elements.

I would also like to highlight some documented tear down of the robomaster in order to let the others understand better how some "alreadu built" parts are made :

https://fccid.io/SS3-RMS11902/Internal-Photos/Int-Photos-4313637

https://hackaday.io/project/167276-dji-robomaster-s1-hacks
2019-12-13
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DJI Stephen
DJI team
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Hello and good day rhoude57 - YUL. Thank you for reaching out and for sharing this information for the DJI Robomaster S1. I hope that our value DJI Robomaster S1 owners will be able to give our there insights with regards to this matter. Thank you.
2019-12-13
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rhoude57 - YUL
Second Officer
Canada
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Napalm78 Posted at 12-13 00:42
Another question : with kind of BLDC motor would you use for Yaw axis ?

I'm currently working on hollow shaft BLDC motor mainly used for gimbal. It allows wiring to pass through so you can plug other elements.

I would expect DJI to re-use the Yaw axis BLDC motor from the RoboMaster S1 to maximize parts commonality.
2019-12-13
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rhoude57 - YUL
Second Officer
Canada
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Napalm78 Posted at 12-13 00:00
Hi !

Great idea, had the same on my side to mount lighter form of the current turret.

Many RoboMaster teams use sliprings to pass signals through the Yaw axis motor so that they can rotate the turret infinitely without having to worry about the wiring that would otherwise run through.
Sliprings are expensive, however, and can be finnicky devices to work with.

As for the connectors, I would hope DJI would drop those custom connectors and go to more standard, i.e. widely commercially available, connectors, for example connectors from the JST family, used widely in the Radio-Controlled vehicle industry... https://en.wikipedia.org/wiki/JST_connector

If I can add, this Universal Turret would need to provide space to optionally attach the RMS1 Intelligent Controller, the camera and the speaker/microphone, since the cannon/blaster would not be included in this expansion kit.
2019-12-13
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Napalm78
lvl.1
France
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rhoude57 - YUL Posted at 12-13 16:04
Many RoboMaster teams use sliprings to pass signals through the Yaw axis motor so that they can rotate the turret infinitely without having to worry about the wiring that would otherwise run through.
Sliprings are expensive, however, and can be finnicky devices to work with.


Hey !

I slightly misunderstood your demand, thought you were going to do it by yourself ! But recommendation is still great for DJI to improve !

You are absolutly right, JST connectors are a must have for every RC devices. If not, at least put simple pins so we can connect simple wiring.

But a thing I'm currently working on is use the current provided turret, which I removed the blaster and speaker from, and put on remaining screw holes some sensors and equipements.

The only thing is, in order to power them, I need to use CAN connectors that are kind of a pain in the a** to get or even to wire and solder without any mistakes. Even if they do want to keep those connectors up, at least provide a generic model we can use.
2019-12-15
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Duane Degn
First Officer
Flight distance : 622234 ft
United States
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Napalm78 Posted at 12-15 04:20
Hey !

I slightly misunderstood your demand, thought you were going to do it by yourself ! But recommendation is still great for DJI to improve !

I agree the CAN connectors are a pain but the turret does include and extra connection at the top. If you've removed the blaster, you can also use its CAN port for power.
I haven't been able to find matching connectors anywhere but 0.1" pitch headers will work on the connector. A 2x2 header like this one should work reasonably well.

You can use the battery power (about 12V) to power devices.
Slip rings are cool but I don't think they're essential. The turret has 540 degrees of motion if the software would allow it. Without a slip ring, you'd need the code to flip the turret back around 360 to continue tracking an object. This of course could be a big problem but at least the turret doesn't have any blind spots.
The robot body could rotate as an object is tracked in order to keep a target within the turret's range of motion. The direction of travel could be maintained as the robot rotates thanks to the Mecanum wheels. I don't have an example of a Mecanum robot rotating while travelling in a straight line but I did program one of my omni wheeled robots to do this.

The S1 should be able to travel in a straight line while rotating. This feature could be used instead of a slip ring in order to allow full rotation of sensors on the turret.
Does your turret behave correctly without the blaster? I've found I need a significant and balanced weight to replace the blaster in order to have the turret behave correctly.

I've considered replacing the center tilt section of the turret with my own platform. The light grey tilt section is a bit of a pain to remove but it's certainly possible to do so. I think there are lots of geometries which would be more useful when mounting cameras and sensors than the current tilt mechanism's geometry.
Here's a photo of the tilt section I'm considering replacing with a different structure.

(The part above is shown upside down.)
The turret's IMU is located on the PCB which controls the tilt motor. I don't think the Intelligent Controller(IC) has its own IMU so the placement of the IC isn't very important. Of course it needs to be close to the camera (if the original camera is used) and the antennas should be positioned to allow a good signal.
The new platform would be secured to the two pivot points of the tilt mechanism.
One side would be secured with three screws to this metal part:

The other side of the platform would need a place to secure the other pivot mechanism.

A platform better suited for various applications could be made and installed.
One benefit of just replacing the tilt mechanism is most of the original turret hardware could could be used. Including the two brushless motors.
One downside of installing such a platform would likely be a voided warranty.

2019-12-15
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MarkusXL
Second Officer
United States
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Indeed the S1 is capable of spinning while travelling in a straight line, or a curved line, or even in a sinusoidal path.

I have dabbled with code to allow such movement, all involving sending continuously variable inputs to the Mechanum Wheel algorithm, posted early in this forum.
2019-12-16
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