Adding Support for New Damiao Motor: DM-J6248P-2EC

[yosh617]

Describe the feature you want

I am planning to add support for the following Damiao motors:

• DM-J6248P-2EC

(Other models are also under consideration)

I have a couple of questions about how to correctly integrate new motors into OpenArm.

1. Files that need to be modified

From what I understand, when adding a new motor, I only need to add the parameters to:

include/openarm/damiao_motor/dm_motor_constants.hpp

And I do not need to modify the CAN interface or other lower-level communication code.
Is this understanding correct?

2. Assigning new MotorType values

I see that the current MotorType enum uses values from 0 to 12.

When adding new motors:
How should I assign new MotorType numbers?

Is there any rule or recommended ordering?

[kou]

1. Files that need to be modified

Yes. We must not need to change include/openarm/{can,canbus}/ for this improvement.

Users who want to use DM-J6248P-2EC, they just passes the motor type of it to openarm::can::socket::OpenArm::init_arm_motors().

2. Assigning new MotorType values

We can just use 13 for DM-J6248P-2EC something like:

diff --git a/include/openarm/damiao_motor/dm_motor_constants.hpp b/include/openarm/damiao_motor/dm_motor_constants.hpp
index 7299c81..4558c42 100644
--- a/include/openarm/damiao_motor/dm_motor_constants.hpp
+++ b/include/openarm/damiao_motor/dm_motor_constants.hpp
@@ -33,7 +33,8 @@ enum class MotorType : uint8_t {
     DMH3510 = 10,
     DMH6215 = 11,
     DMG6220 = 12,
-    COUNT = 13
+    DM6248 = 13,
+    COUNT = 14
 };
 
 enum class ControlMode : uint8_t { MIT = 1, POS_VEL = 2, VEL = 3, TORQUE_POS = 4 };

We should not change the existing values because it breaks API/ABI compatibilities. We don't want to break API/ABI compatibilities as much as possible.

[euyniy]

In fact, motor limits should also be needed at the corresponding indices

openarm_can/include/openarm/damiao_motor/dm_motor_constants.hpp

Lines 97 to 112 in 947e896

	inline constexpr std::array<LimitParam, static_cast<std::size_t>(MotorType::COUNT)>
	MOTOR_LIMIT_PARAMS = {{
	{12.5, 50, 5}, // DM3507
	{12.5, 30, 10}, // DM4310
	{12.5, 50, 10}, // DM4310_48V
	{12.5, 8, 28}, // DM4340
	{12.5, 10, 28}, // DM4340_48V
	{12.5, 45, 20}, // DM6006
	{12.5, 45, 40}, // DM8006
	{12.5, 45, 54}, // DM8009
	{12.5, 25, 200}, // DM10010L
	{12.5, 20, 200}, // DM10010
	{12.5, 280, 1}, // DMH3510
	{12.5, 45, 10}, // DMH6215
	{12.5, 45, 10} // DMG6220
	}};

[yosh617]

Understood. Thank you.

I have one question regarding the motor limits.
For example, in the datasheet of DM-J4310-2EC (page 9)

The no-load maximum speed is listed as 200 RPM, which converts to about 20.94 rad/s.

openarm_can/include/openarm/damiao_motor/dm_motor_constants.hpp

Lines 90 to 100 in 947e896

	// Limit parameters structure for different motor types
	struct LimitParam {
	double pMax; // Position limit (rad)
	double vMax; // Velocity limit (rad/s)
	double tMax; // Torque limit (Nm)
	};
	// Limit parameters for each motor type [pMax, vMax, tMax]
	inline constexpr std::array<LimitParam, static_cast<std::size_t>(MotorType::COUNT)>
	MOTOR_LIMIT_PARAMS = {{
	{12.5, 50, 5}, // DM3507
	{12.5, 30, 10}, // DM4310

However, in the code, the limit is set to 30.
Also, that datasheet shows a maximum torque of 7 N·m, but the parameter in code is set to 10.

This can also be seen in other motor parameters.
Why is there such a difference?
Is there a specific rule for setting limits (e.g., rounding to the nearest 10, considering safety margins, etc.)?
I would like to understand the reasoning so I can correctly set the limits for the new motors as well.

[kou]

You have DM-J6248P-2EC, right?

Could you try with the catalog spec values for now? If they don't work, let's adjust them.

[yosh617]

Thanks for your reply!

Sorry, The DM-J6248P-2EC has not arrived yet, so I cannot test it right now.
However, with the other motors I have, they work both with the catalog spec values and also with the higher limit values defined in the code
(of course, the actual performance does not exceed the catalog specs).

So I think the DM-J6248P-2EC will also work.

What I would really like to understand is whether there is any rule or guideline for setting these limit values in the code.
For example:

• giving some margin above the catalog values,
• rounding to clean numbers,
• or applying some internal safety factor.

If there is a specific policy or reason behind these values, I would like to follow the same approach when adding new motors.

[kou]

I understand that you want to know the guideline but @euyniy is busy for now. Could you start with catalog spec values? We can adjust values later.

[yosh617]

Thank you for the guidance.
Once the motor arrives, I will begin testing it using the catalog specification values.
After I am able to run the experiments, I will share the results here in this issue.
Thank you again for your support.

[euyniy]

Sorry for the late reply. I think catalog values should work. I don't have 6248 motors at my command tjp welcome to PR after you have tested!!

[MichalN12]

Hi there, would it be possible to add support for the DM-H65-1EC wheel motor? I know you all are busy, but I have the physical motor with me and would be very happy to help test any code if a maintainer is able to look into it. Thanks for all your hard work on this project!

[kou]

Could you open a separated issue for DM-H65-1EC for easy to track?

[MichalN12]

Will do right away. Thanks!