ros-melodic-ros-controllers-cartesian : Depends: ros-melodic-twist-controller but it is not installed

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It is not clear what question you are asking.

When i run sudo apt-get upgrade, i get unmet dependencies error, even after i run "apt --fix-broken install" i get the same error

Have you tried to install the missing dependency? sudo apt install ros-melodic-twist-controller

@osilva i have tried "sudo apt install ros-melodic-twist-controller" it gives the following error

Unpacking ros-melodic-twist-controller (0.1.4-1bionic.20210921.212715) ...
dpkg: error processing archive /var/cache/apt/archives/ros-melodic-twist-controller_0.1.4-1bionic.20210921.212715_amd64.deb (--unpack):
 trying to overwrite '/opt/ros/melodic/lib/libtwist_controller.so', which is also in package ros-melodic-cob-twist-controller 0.8.12-1bionic.20210921.230048
Errors were encountered while processing:
 /var/cache/apt/archives/ros-melodic-twist-controller_0.1.4-1bionic.20210921.212715_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

What's your OS version? What's the output of uname -a? If you have Ubuntu20.04 you shouldn't be installing melodic since that requires 18.04.

Use noetic instead: http://wiki.ros.org/noetic/Installati...

@bergercookie im using Ubuntu 18.04 LTS (Bionic Beaver)

uname -a
Linux kannan-Lenovo-ideapad-320-15IKB 5.4.0-86-generic #97~18.04.1-Ubuntu SMP Sat Sep 18 03:11:22 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

Those error messages indicate a conflict between the two apt packages ros-melodic-cob-twist-controller and ros-melodic-twist-controller. I would try to purge cob, which hopefully will not remove any packages you actually want to use. Make sure you read and understand the list of packages about to be removed before you confirm the purge.

sudo apt update
sudo apt purge ros-melodic-cob-twist-controller
sudo apt --fix-broken install

@Mike Scheutzow when i try to purge i get the following error

 Reading package lists... Done
    Building dependency tree       
    Reading state information... Done
    You might want to run 'apt --fix-broken install' to correct these.
    The following packages have unmet dependencies:
     ros-melodic-cob-cartesian-controller : Depends: ros-melodic-cob-twist-controller but it is not going to be installed
     ros-melodic-cob-twist-controller-dbgsym : Depends: ros-melodic-cob-twist-controller (= 0.8.12-1bionic.20210921.230048) but it is not going to be installed
     ros-melodic-ros-controllers-cartesian : Depends: ros-melodic-twist-controller but it is not going to be installed
     ros-melodic-twist-controller-dbgsym : Depends: ros-melodic-twist-controller (= 0.1.4-1bionic.20210921.212715) but it is not going to be installed
    E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or specify a solution).