Can we use ethernet cable instead of coaxial cable without adaptors.?
For motion applications, one should really use "flex-rated" cables.  It really does not take long for 'typical' cables to fail when exposed to repetitive motion applications.

Flex cables are expensive, but they will solve your problem.  Patching in other cable types may give you a bit more longevity, but the cables will still fail.

Flex-rated cables are designed such that not only the inner conductors last longer (more/finer strands, and additional non-conductive elements), but also the outer jackets can slide against each other and not chafe as much.

Flex cables are available for single and multi-conductor cords, as well as coaxial cable.  You can find them by searching for "Flex cables" or "continuous motion cables".