EuRoC Forum

[kaust]

Hi,

In response to the service call MoveAlongJointPath, I get the error message: ipol_init returned error -10. stop_reason is empty.
Does it assume that joint_names are in a particular order?

[fschmidt]

this is probably caused by some weird combination of acceleration/velocity and/or via-point distances.

can you send us which path, verlocity and acceleration you commanded?

[kaust]

Thanks, I corrected the max-velocity and put some nominal values for max-acceleration and now it works as shown below.
But can you tell me where the max-acceleration values come from? The max-velocities are of course returned when the simulation is started.
Do we need to back-compute max-accelerations from the max-torques?

Code: Select all

[ INFO] [1413723806.023565871, 41.594000000]:     axis_x:    -0.26963     [max-speed 0.50000] [max-acceleration 0.50000]
[ INFO] [1413723806.023602278, 41.594000000]:     axis_y:    -0.22476     [max-speed 0.50000] [max-acceleration 0.50000]
[ INFO] [1413723806.023635044, 41.594000000]:     lwr_joint_1:    1.50016     [max-speed 1.74530] [max-acceleration 0.50000]
[ INFO] [1413723806.023667530, 41.594000000]:     lwr_joint_2:    -0.65890     [max-speed 1.74530] [max-acceleration 0.50000]
[ INFO] [1413723806.023699500, 41.594000000]:     lwr_joint_3:    2.03361     [max-speed 2.79250] [max-acceleration 0.50000]
[ INFO] [1413723806.023741958, 41.594000000]:     lwr_joint_4:    -0.94132     [max-speed 2.79250] [max-acceleration 0.50000]
[ INFO] [1413723806.023782515, 41.594000000]:     lwr_joint_5:    1.70029     [max-speed 4.71240] [max-acceleration 0.50000]
[ INFO] [1413723806.023815486, 41.594000000]:     lwr_joint_6:    -1.32559     [max-speed 3.66520] [max-acceleration 0.50000]
[ INFO] [1413723806.023847663, 41.594000000]:     lwr_joint_7:    0.00001     [max-speed 3.66520] [max-acceleration 0.50000]
[ INFO] [1413723806.023884127, 41.594000000]:     gripper:    0.00019     [max-speed 0.50000] [max-acceleration 0.50000]
[ INFO] [1413723806.023921358, 41.594000000]:     cam_pan:    -0.00000     [max-speed 1.74530] [max-acceleration 0.50000]
[ INFO] [1413723806.023953903, 41.594000000]:     cam_tilt:    0.78525     [max-speed 1.74530] [max-acceleration 0.50000]
[ INFO] [1413723825.329775436, 45.565000000]: Execution completed: SUCCEEDED


[fschmidt]

the max-acceleration per joint depends on the robots current state (position/configuration, velocity ...), the attached masses behind that joint and the max allowed joint-torque.

we didn't set a hard (always guaranteed) limit for the max acceleration per joint so that teams might be able to achieve high task-space accelerations by carefuly planning in the robots configuration space.

so, yes: if you want to know the max achievable acceleration you would have to compute it with the help of a dynamics model.

but each of the simulated LWR joints does atleast 600[deg/s^2] (without additional object-load).

by looking at the motion-generator code that returned "ipol_init error -10" i see that this message can only be achieved by specifying a max-acceleration of 0 or less.