Read and apply limits from the URDF - #35
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…l to coupled coordinates - this needed an additional function added to the kinematics translator
pvonwirth
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pvonwirth
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You do not verify or ensure maximum joint limits within the couplend_..._interface class.
Please correct me, if I'm wrong.
But with only the motors observing / limiting themselves, this does not observe the actual maximum joint velocities. (Due to coupled kinematics)
Thus, I would first of all suggest to limit the joint commands where we still have joint commands.
The second issue is more critical: If one motor limits its commanded velocity and others do not, this may lead to involuntary absolutely uncommanded and undesired movements, especially with coupled kinematics, making the system unpredictable.
This is a state that we, i.m.h.o. should absolutely avoid.
A better approach is to detect 'overvelocity' and limit the entire robot equally, so that the entire robot becomes slower but the position trajectory stays invariant.
Limiting torques is even a more difficult problem to discuss.
I would put the hardware limits (with safety margin as already is intended) as absolute error barrier, freezing the robot if a violation is detected on that level. Because it should have be handled before.
Maybe this is worse a discussion. Maybe also together with @nferber to define actions the robot is allowed to take and the ones it should never do when applying safety limits.
| { | ||
| // Factor by which we extend the hard limits so that what an application uses as limit for the input and what we use as | ||
| // hard safe factors is a bit scaled | ||
| inline constexpr double velocity_range_extension_factor = 1.1; |
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Do you think 10% is "a bit" scaled ?
| if (!drive_->getGearboxRatio(configured_gear_ratio_)) { | ||
| RCLCPP_ERROR_STREAM(logger_, "Failed to obtain gear ratio"); | ||
| // Throw as this is critical because we cannot use it to calculate the proper maximum motor velocity | ||
| throw std::runtime_error("Failed to btain the gear box ration of drive: " + get_name()); |
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- type: "obtain"
- I think that drive internals such as gearbox ration should not be exposed to the outside. This is something for the drive and its firmware and noone else ...
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driverpackages (added transform)Discussion points
I don't really like the urdf tags as they are fixed in what we can pass there. For example adding a power limit would not be possible right now but somewhat desirable ?