Issues with FT-300S Force Torque Sensor moving along a smooth trajectory

xqcheng

Hi, I have a FT-300-S force torque sensor connected to a xArm 6 and controlled via the xArm ROS and robotiq_ft_sensor SDK. I am trying to create a smooth trajectory that will exert a constant force of 1 N in the Z direction (i.e., downwards force) and move in a combination of X and Y direction (rotary motion) upon contact with a surface. Waypoints was collected along the oval trajectory. However, when I tried to have xArm moved along the waypoints collected with compliance control activated, the xArm 6 was bobbing up and down as it moves along the waypoints (see video attached). I'm thinking there's some issue with certain parameters that's being set or that there should be something that I overlooked. Would anyone happen to have any ideas?

bcastets

I am not familiar with xArm. I looks like your robot over react. If you are using xArm functions to do this force control application, the robot maker suppor team may be able to help. You may also find some information about to make adjustments in the robot manual.

xqcheng

Hi! Do you have some ideas on what may have caused the over-reaction? The robot arm is using forward dynamics compliance control for the force control loop. Yes I am also contacting the robot maker support team as well though any potential inputs to help resolve the issues are welcomed!

In addition I also have the following questions on the robotiq sensor:

1. On the specs for the force torque sensor, it says that the contact detection threshold is 1N. Does that mean that a contact is only detected when the force exerted upon hitting a surface exceeds 1N? 

2. Related to the above question, if I would like to have the robot arm exert a constant force of 0.3 to 0.5N on a surface, would that pose any difficulty for the force torque sensor since the force to be exerted is pretty low

Thank you!

bcastets

It is very challenging to apply a force of 0.3 or 0.5N under force control.

Threshold of 1N means that to differentiate 2 forces you need to have at least 1N difference. For force control we usually use force arround 5N.
0.3N is equivalent to 30g. It is very low.
5N is equivalent de 500g.

The robot may also be over reacting because the force requested is too low.

robotq

xqcheng said:

Hi, I have a FT-300-S force torque sensor connected to a xArm 6 and controlled via the xArm ROS and robotiq_ft_sensor SDK. I am trying to create a smooth trajectory that will exert a constant force of 1 N in the Z direction (i.e., downwards force) and move in a combination of X and Y direction (rotary motion) upon contact with a surface. Waypoints was collected along the oval trajectory. However, when I tried to have xArm moved along the waypoints collected with compliance control activated, the xArm 6 was bobbing up and down as it moves along the waypoints (see video attached). I'm thinking there's some issue with certain parameters that's being set or that there should be something that I overlooked. Would anyone happen to have any ideas?

Hi，have you solve this problem？ I am also doing some research about this