Hi Alex,
Take configs/sim/sim_xyzbc.ini as an example:
- it has JOINT_* sections for joint parameters
- its AXIS_* sections are basically empty
- it take gantrykins
emccanon.cc::getStraightAcceleration() was called for trajectory planning.
It calls emcAxisGetMaxAcceleration() for AxisConfig[axis].MaxAccel, the
MaxAccel of corresponding axis.
MaxAccel is set by emcAxisSetMaxAcceleration() at iniaxis.cc::loadAxis().
In this configuration, it doesn't define MAX_ACCELERATION for AXIS_*
sections. Therefore, the MaxAccel is set as the 1.0, the
DEFAULT_AXIS_MAX_ACCELERATION.
As a result the velocity/acceleration is way too small while running G-code.
IMHO, we can calculate the MaxAccel of each AXIS(x,y,z,a,...) based on
kinematics and corresponding JOINT settings.
What's your opinion?
Yishin
On Mon, Nov 9, 2009 at 4:29 PM, Alex Joni <[email protected]> wrote:
> Hi Yishin,
>
> actually in this case (emccanon.cc) it is correct.
> The calculations you are looking at are for the X axis. The X axis is the
> same no matter what machine you have.
> It is further down (in the motion controller, trajectory planner) that this
> X move would have to be scaled further based on _joints_ limits.
>
> Regards,
> Alex
>
>
> ----- Original Message -----
> *From:* Yi-Shin Li <[email protected]>
> *To:* EMC developers <[email protected]>
> *Sent:* Sunday, November 08, 2009 2:01 PM
> *Subject:* Re: [Emc-developers] the trajectory planner might not be
> suitableforany machines with non-trivial kinematics
>
> Hi Alex,
>
> I've pulled the joints_axes3 branch, built and tried it.
> In this branch, the *getStraightVelocity()* and *getStraightAcceleration()
> *
> on emccanon.cc are not suitable for non-trivial kinematics yet.
>
> I will file a feature request on SourceForge later.
>
> Regards,
> Yishin
>
> On Thu, Nov 5, 2009 at 2:22 AM, Alex Joni <[email protected]> wrote:
>
>> Hi Yi-Shin,
>>
>> unfortunately you are correct.
>> There are some problems in the current version of emc2, that joints
>> (motors) and axes (carthesian directions) are mixed in a couple of places.
>> There is ongoing work (on the joints-axes3 branch) to fix this.
>> But it's a lot of work (in a lot of layers and places), so there is no
>> fixed timeline when it will be useable.
>>
>> Regards,
>> Alex
>>
>>
>> *From:* Yi-Shin Li <[email protected]>
>> *Sent:* Wednesday, November 04, 2009 6:13 PM
>> *To:* emc-developers <[email protected]>
>> *Subject:* [Emc-developers] the trajectory planner might not be suitable
>> forany machines with non-trivial kinematics
>>
>> Hello emc-developers,
>>
>> I was digging into an issue for SCARA Robot controlled by EMC2. That is,
>> the angular acceleration for the first 2 joints is way too larger than the
>> one
>> set by its configuration file. After carefully analyzing the dumped trace,
>>
>> I found it might be caused by misleading trajectory planning results.
>>
>> I then found an interesting issue for the trajectory planner, i.e. it
>> might not
>> be suitable for any machines with non-trivial kinematics. Please take a
>> look for the following code at *getStraightAcceleration()* on
>> emccanon.cc:
>>
>> tx = dx? (dx / FROM_EXT_LEN(AXIS_MAX_ACCELERATION[0])): 0.0;
>>
>> For non-trivial kinematic machines, such as SCARA, the dx is contributed
>> by
>> several joints other than AXIS_0. However, the above code assume that
>> it only depends on AXIS_0, which is not true for those machines.
>> Therefore,
>> the calculated accel/velocity for trajectory planner may be incorrect.
>>
>> Is my understanding for above statement correct?
>>
>> Yishin
>>
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