Yet something with follow target still isn’t behaving right, works 98% of the motion but still has jitters that don’t make much sense to me.
Those ‘jitters’ always lead me to look in the console for those pesky ‘Cyclic Dependencies’…there are 2 on the file you posted.
Hello one and all from my sick bed!!!
Please see this I have posted a rig there to do this without all the Cyclic Dependancies, endless constraints, etc. etc.
Cheers ,Clock. 
Hi Sir!
This rig does not “jitter” for me so in that regard it looks good, have you updated it by an chance?. I would make an IK for the link to the second/end arm rather than your Locked Track though, just so I can make the whole link to the hydraulics one complete chain. I have posted in the linked thread above, my solution to parallelogram rigs.
Cheers, Clock.
EDIT:
Also your method of doing cylinders is not the best, I have shown a way in the blend file in the linked thread. You could use a single Stretch To rather than the IK if you like, just make sure the piston and cylinder bones do not inherit scale from the stretch/IK “stroke” bone.
Sorry all, for not getting back to the comments and help over the past week or two. I have been having major problems with Virgin Media broadband. Typical for large organisations they over sold broadband in my area and generated utilisation issues for the local distribution hub. Their service has been bad for the past two months but the past two weeks were impossible with the connection continually dropping out at all but the most unsocial midnight hours. Their customer service wasn’t much better with insultingly low amounts of compensation offered for the very bad service. Still the local distribution hub has been upgraded today and all seems well, though I doubt I will stay with their extortionately overpriced service.
With internet down I set my PC to render a short animation of the robot stacking bags onto a pallet, mainly to get a feel for how the scene will look when finished. A lot more detail to add yet but the video below gives a good feel for what I am intending.
Thanks for the demo rigs I will have a look at them over the next day or two as I catch up.
Cheers
Rob
@robbur, looks good, until I googled the real machine, I had no idea what they were for,:o, yours looks just like the real thing.
@ pauljs75_
By the way, the steel frame building and palletizer robot are looking pretty neat. Going to put in other stuff like fork-lift bots and industrial shelving too? Also those little safety cage things (not really a cage, but a tube structure that lets you know where to stay clear) and warning lights, along with the floor markings? (Maybe I’m probably a bit early in mentioning that stuff though.)
You must have been reading my mind whilst I was modelling the safety barriers, I will be adding more details like hydraulic hoses, cables and electrical control panels etc. If time permits I might even add a forklift loading and unloading pallets.
Though I have been modelling with Blender for more than 12 years I am still very new to animation and rigging so all your help is very much appreciated.
@ clockmender Thanks for posting your rig and pointing me to the animation support post on this setup. I am still struggling to understand how to build a rig that operates from one control point. My setup with a rotation empty and an arm position empty works okay but I will keep trying for something a little more refined. Hope you get well soon.
@ ajcdfin thanks and glad you like the progress so far.
This setup seems to work with one control empty for both rotation and position.
The linkage will be IK driven off the main arm and base.
@robbur, Your revised set-up works just fine 
Just one thing, if you have that last bone (.004) parented to the IK bone (.003), you won’t need that ‘limit rot’ const if you have ‘unchecked’ ‘Connected’ and ‘Inherit Rotation’. I would add a ‘Limit Location’ const to the ‘Empty’ so you don’t have to chase it too far 
