CAN Newsletter special issue bauma 2007

CANopen on-board PCs in construction equipment

In March 2005, John Deere presented a system concept for the control of construction equipment. The system targets integration of advanced positioning functionality and general, CAN-based machine control features. Work quality and efficiency can be boosted by applying high precision positioning systems, so called ‘autoblade’ systems, in construction equipment such as dozers and motor graders. The systems consist of a GPS receiver, laser detectors, an ‘autoblade’ micro-controller and an on-board computer that runs the application for geographical data. This on-board computer typically runs on Windows CE, Windows XP, or Windows XP Embedded. Autoblade systems can be fitted to basically any machine type as a commodity add-on system. The system is partly integrated with the machine control system so that the blade of the machine can be controlled automatically. This means that the driver can focus on handling the vehicle while the autoblade system ensures that the soil, gravel or shingle is shaped correctly.
John Deere’s TMC (Total Machine Control) system focuses on integration and takes autoblade functionality to the next level; the on-board PC and electro-hydraulic subsystem is supplied as a component in the machine control system from the factory. This means that the PC can be used for a bundle of features:

• Machine diagnostics via CAN network number 1 (J1939),
• Display of meters and gauges via CAN network number 1,
• Video, display of rear-view camera image, and
• Autoblade functionality via CAN network number 2 or RS-232.

Controls and sensors for mobile machines

We cannot imagine life today without electronics in mobile machines. Many necessary and convenient functions could not be implemented without electronic systems. In contrast to electronics in consumer goods the requirements for components for mobile use are considerably higher in order to achieve sufficient operational reliability in all situations.
The mobile machines and installations are often specially tailored to the applications and thus relatively expensive. High uptime of these cost-intensive machines and installations therefore requires extensive, easy and safe system diagnosis for fast direct fault location by the operators. Safe and clear operating concepts via displays adapted to the respective operating situation can help to avoid incorrect operation. The operating and system states must be stored for statistics and documentation via an operational data log.
Furthermore, networking the system components by a bus system is required to reduce wiring complexity. This enables a decentralized arrangement of the powerful input/output modules in the direct vicinity of the sensors and actuators. This means they are mounted where the data is produced or needed. In addition, the components must be easy to handle for mounting and in case of service. The mechanical design, plus easy and clear integration during programming ensure the above is achieved.
Last but not least the components and devices used must withstand the extreme mechanical, climatic and electrical requirements and reliably fulfill the assigned tasks for a long period. All above-mentioned requirements aim at developing reliable, competitive and cost-optimized machines.

CANopen is a trend on elevating work platforms

As in other mobile vehicles there is also a trend for elevating work platforms to use electro-hydraulic control systems with CAN interface and CANopen communication. This increases operational safety, ensures higher flexibility and lower assembly costs. The automation system digsy compact, which has been developed especially for mobile applications comes with CAN interface and CANopen protocol. It is particular suitable for mobile applications because of its extremely safe data transmission and its high availability.
With the network components, offered by Inter Control you can build up a decentralized automation system. The CAN components are equipped with a robust aluminum housing, which is resistant against salt water, high pressure water and rock fall. For that reason these components can be mounting directly on the outside of the vehicle without any additional switch cabinets. The system is freely programmable and EMC, vibration and shock proofed. The working temperature range is from -40 ˚C to +85 ˚C. This is of course also valid for the CAN-nodes, which assume further tasks of the control system.
Concerning the application technology you can achieve many advantages on an elevating work platform by using the automation system. The main problem in the past was the huge number of wires between the basket and the elevating platform vehicle. Because of the little space available inside the boom, the number of wires had to be decreased.
This problem was solved by using the automation system with its two-wire CAN system and the CANopen protocol. The unique advantage compared to a standard wiring or older bus systems such as RS-485 is that many bus members can be connected immediately. The CAN devices such as controllers or other nodes can be mounted on a location together with many sensors, actuators or valves. Thus you can avoid running long cables with many wires through the vehicle to a central place. The effort for the wiring of the vehicle can thereby be decreased dramatically.