2009 Round Up.

This is our last day for 2009, and a good point to finish on, we have the leg running under control of the HexEngine, currently the leg is still missing the metatarsus ram which arrived today, the coxa ram is fitted but needs to be plumbed up. Finishing the hydraulics for the test leg will be our first job in the new year. I'm starting to wonder if we actually needed low friction seals on our rams, it seems there is a fair amount of leakage across the piston seals, that may be causing some undesirable issues. TBC.

The load pin has arrived, so we will also look at fitting this upon our return. I have yet to decide how I am going to wire this in to the HexEngine, I think I will need to modify the FACU box to take auxiliary analogue inputs, or create a new box that will also sit on the 485 bus which will act as an analogue/digital I/O module.

There is much work to do on the FACU control unit, safety features to check, PCB to finalise etc. Also the data stream mode needs to be added to the HexEngine, along with the position/status report packet back from the FACU.

A fine adjustment..

After all that beautiful Laser and Waterjet CNC cutting.. it always comes back to a power file :)

Having run the leg for a while, we noticed a little chafing on the hoses, so a fine adjustment with the power file for now, and some retro fitted rollers should sort things out.

Second Cylinder Delivery

Our second delivery of cylinders arrived this morning, we now have the two 40mm MIL type cylinders, one for the tibia, and one for the coxa. Unfortunately we still can't mount the coxa ram as we still don't have the ram mounts which were accidentally left off the order. We will get the tibia ram piped up and commissioned today, we have Jerry coming in tomorrow for his first visit since the project started. It would have been nice to show him a complete working leg. If we had had the complete Parker order on time, this would have been the case!!

The leg lives!! Very EXCITING :)

Yes, today we have the leg moving under hydraulic control.. Ok, so its only one joint of one leg, but it feels like a major mile stone, and also slightly terrifying :)

We started with simple open loop control of the valve at 50bar, so that we could drive the cylinder from one end to the other. This was working pretty well, although a little underpowered on the annulus upstroke when lifting the weight of the leg. However, we were only running at 50bar. At first we had the tibia down in contact with the floor, I drove the leg in the wrong direction, eg, towards the floor. To our surprise even at this low pressure the leg started to move our test rig which is bolted to the floor and wall.. that's the terrifying part :)
 

Next we got the leg running under closed loop control and at a higher pressure of 75bar, it's all going pretty well considering its our first hydraulic test, however, we have quite a bit of air in the system which isn't helping. We will spend more time on Monday bleeding the system and give the leg a power test. Josh has an idea of using our engine hoist to check the femur power.. kind of hoist versus leg.. to be continued.

Manifold Assembly

Today we assembled the test manifold, to start with we are going to test the cheaper 4WREE valves, which we have two of. We will then install and the 4WRPE valves when get the rest of the cylinders and need to test the complete leg.

We asked a few hydraulic experts how tight we should do up the fittings, most of which are 3/8" and 1/2". The answer seemed to be tight.. chuffing tight! hence the big spanner!

The first hydraulic cylinder arrives!

We have just received delivery of the first of our hydraulic cylinders from Parker. Our order has been some what delayed, and sligtly mixed up, so they have shipped this cylinder ahead of the rest of the order to get us going. We have the Femur cylinder, the largest of the cylinders on the Mantis.



We picked up some garden hose so that we can lay out our hose routing and measure our hydraulic hose lengths, we will then order them from hosemaker, a very useful on-line service with a very helpful chap Roger who has been dealing with our endless questions. :)

Test leg assembly together :)

Here it is, our first look at a near complete leg assembly, without the rams and the metatarsus/foot, but most of it is there! Pretty exciting to see this together and get an idea of scale, You can see from the images of Josh and I sitting in the approximate driving position.

We must be Bonkers!!

Test Leg Frame is Finished!

Josh finished the test leg rig today, this means we will hopefully be able to assemble the coxa and mount the leg by the end of this week :) Looking forward to seeing it come together!

Servo Libraries

I have spent the week writing code for the HexEngine servo drivers. I'm trying to make the servo library for both the RX10 and Hydraulic FACU box interchangeable. Hopefully this means I will be able to switch the engine back to the 1/10 test rig to confirm new features, without too much hassle! Well at least that's the plan.

Got the EDU licence dongle for Webots this week, fortunately it is running our simulation fine, so I'm glad I didn't fork out for the Pro version, although no doubt I will need it at some point in the future.

Another Setback!

I've been chasing up the hydraulic rams from Parker this week, we were hoping they would arrive by the end of November! Having spoken to Glen our rep from Parker, they think the rams will be with uds by 15th December, a little disappointing as we hoped to get the hydraulic rig running before Xmas. Also it turns out that one of the rams and two brackets won't be in the first shipment?? Apparently they were not ordered, even though we have paid for them! Another virtual item on the "Others Shelf Of Shame"!

God bless Ebay!

I can't quit remember how I stumbled upon these, but I'm sure glad I did! I picked up seven hydraulic pressure transducers for £20 each!! :) well happy with that. We are not sure if we will definitely use all seven yet, but I needed at least one to measure the system pressure, and possible one on each femur ram. I got a good price from SICK for their pressure sensor, of £80 each, so another good saving by picking up these brand new Parker units for £20 each :)