Projects

To have better control of the system and also to save energy there should be some way to be able to control the variable displacement pump pressure. This can be accomplished by controlling the pressure in the feedback input ( X ) of the pump controller as seen in the pump documents.

One way to have couple steps in the control could be to use CVGC-3 and DG4V-3-0C valves from Vickers that were found from some old equipment.

The circuit should be like this then:

Another alternative could be proportional control with valve like Vickers KCG-3 pressure relief valve.

CVGC-3 and DG4V-3-0C were found from some old equipment but from a bit difficult place so getting access to them would require disassembling part of the machine. Quote for a new KCG-3 wasn’t that cheap either…

Then I got the chance to get a Bosch-Rexroth ZDRE 6 pressure reducing valve for a fraction of the quoted price for KCG-3 so it will be the planned valve for controlling the pump now. It is not the most optimal solution but should be possible to fit it in there.

Head module for the Keto 51 project will be located in the harvester head itself. The purpose of this module is to control the hydraulic valves and read the sensor inputs. It will be connected to the main control system using CAN bus. This way the wiring between the head and the base machine can be kept simple as only power and two wires for the CAN communication is needed instead of wiring all the valves and sensors all the way to the base machine.

Locating the electronic module to the head exposes it to quite challenging environment so there might be some additional problems to solve because of this. Vibration is probably the largest problem here.

The module will use AT90CAN128 microcontroller and also XC9572XL CPLD for the quadrature counters and output diagnostic monitoring.

Here is a photo of a partially assembled board. The board was designed and sent for manufacturing in the last minutes before leaving for vacation so it’s a bit of a mess in some ways and some problems have been found already. But it should work for prototyping.

Finding the right connector to interface the module to the outside world can be challenging too. For this first prototype a Molex Minifit Jr connector was chosen as it’s cheap and easy to get and should be quite easy to make changes compared to some other connectors out there.

But a better connector would be nice later. One alternative could be Econoseal from Tyco. This one is available in small quantity from the VEMS Shop. Another tempting connector is the Ampseal series which looks like it would be easier to make a sealed case with it. Just haven’t been able to find a place that would sell these in small quantity. If someone has suggestions for a possible sealed connector to use I’d be glad to hear of them.

Hydraulic pump to be used is Bosch Rexroth A10VO 71 with DFR1 control.

A10VO datasheet

A10VO datasheet alternative link

DFR1 control:

Click for more details:

I posted couple photos with the title “New project” a while ago. In the photos was the hydraulic block of a Keto 51 harvester head. Might not tell much if you’re not already familiar with this kind stuff though. Manufacturers website.

Here is also a video of it in action to give a better idea of what it does. (10MB Quicktime)

The video originally comes from the Kronos videogallery but as it’s not available there anymore I have provided a local copy.

Target here would be to build a working system around a used Keto 51 harvester head. That would include building the electronics that control the hydraulic valves and also the rest of the hydraulic circuitry needed like the pump.

The electronics consists of a few different modules connected with CAN bus. The main brains of the system runs on top of the ADS Graphics Client Plus board. This module runs Linux with the RTAI real time system. Basically Linux runs as a low priority task on top of the realtime scheduler so it doesn’t disturb the parts needing more real time response. User interface and file IO for example are left for Linux to handle. For user interface a 320×240 pixel EL panel is used. This board should have plenty processing power and resources for future needs.

Another module is for controlling the hydraulic valves and reading sensors in the harvester head. This module should be situated in the head itself to minimize the wiring needed. This module should have the capability of controlling about 15 on/off solenoids and also possible expansion room for couple proportional outputs. For input two quadrature encoders need to be read and some inductive proximity sensors.

Just couple photos of what is coming…

The above will be combined with something else already seen here.