There is a trend of elevated work plat-forms in mobile applications and vehicle-based systems with the use of 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, was developed especially for mobile applications and comes with CAN interface and CANopen protocol. Particularly suitable for mobile applications because of its extremely safe data transmission and its high availability, with the network components offered by Inter Control, it is possible to build a decentralised automation system. The CAN components are equipped with a robust aluminium housing, which is salt water resistant and guarded against high pressure water and rock fall. The components can be mounted directly on the outside of the vehicle without any additional switch cabinets and the system is freely programmable. EMC, vibration and shock proof, 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, many advantages can be achieved 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 avoiding running long cables with many wires through the vehicle to a central place. The effort for the wiring of the vehicle decreases dramatically.
In the vehicle basket, there is a control panel with a monochrome, graphical visualisation system, called digsyCGM (Cockpit-Graphic-Monitor). More comfortable and available with many options is the colour visualisation system digsyCMV (Cockpit-Multi-Vision). With the facility to connect up to four cameras to it, which can be controlled either by events or manually, both the units are automation systems, and freely programmable according to the standard IEC 61131-3. The HMI in the basket shows all operating states of the elevating work platform. For example, the current height and reach either as bar graphs or absolute values. The control panel is also used as a picture guided operating unit. Various functions are generated by icons (symbols) above the function keys, as there are speed adjustments, memory functions or pin code-protected height limitations of the elevating work platform. In case of irregularities in the system, the same would be visualised by the automation system. Due to the possible diagnostics opportunities, expensive downtimes can be minimised.
Additional bus members in the control panel are two analogue CAN joysticks, which cater for sensitive steering. With auxiliary inputs on the CAN control board, additional push buttons are injected to CAN bus. On the CAN bus between the control panel and the basis of the vehicle, a Digsy Compact is located on the basket arm, which besides other tasks is also responsible for the levelling of the basket. It also exchanges data with the CANopen manager. While further controller at the vehicle level serve as a central control system, the automation system takes care of the activation of the hydraulics and the acquisition and surveillance of the sensors. At the same time a redundant load limiting system and the blocking of dangerous areas are integrated. Sensors interestingly examine all relevant operating parameters as there are the angle of the boom and the turntable, the pressure in the boom cylinder, the weight in the basket and the current outrigger configuration. The signals are transmitted to the automation system, which also calculates the respective limit values. Thus it is possible to use the performance of the elevating work platform in an optimal way.
 When the platform comes close to the critical area, the automation system caters for a sensitive slowing down of the movement until the stop. In order to adjust the outrigger configuration to the location, the operator can deploy the outriggers either inside or outside the vehicle outline from the basket. On larger models of elevating work platforms from Wumag Elevant GmbH, every outrigger can be stopped in any position. After the pre-selection of the position of the outriggers they can be moved down semi-automatically per joystick or controller. This results in a torsion free strut of the vehicle. The reach of the basket will be automatically adjusted to the outrigger configuration. A second or emergency panel terminates the lower end of the bus. It is equipped with analogue joysticks, push buttons and LEDs. This panel controls more than 30 LEDs, which visualise functions for the operator. It also transmits commands of almost 20 buttons and two joysticks to the CAN bus. Commonly used I/O modules and wiring would not have been able to achieve this in an affordable way for the customer. This again shows the advantages of the CAN network vividly.
The automation system is serially equipped with non-volatile data memory and a real-time clock. Service data, operating hours and irregular system conditions can be recorded. Additionally, for example, the rental agencies can analyse job data and user data by using the corresponding software.
Remote data transmission Because tele-service offers big advantages for the customers such as short reaction times and cheap after sales service, it becomes more and more popular. For that reason Inter Control offers the digsyServicLink. Via GSM-technology one could get access to the automation system. This connection with a speed of 9.6 kbit/s is suitable for remote diagnostics. The device can be equipped with a GPS receiver. This enables the owner of a vehicle to find out its position any time. By using the tele-service the manufacturer or the rental agency has the chance to investigate the actual state of the elevating work platforms and to solve problems without travelling to the vehicle. For preventive maintenance the vehicle sends a SMS to various phone numbers. Thus you can identify problems in time and there is a chance to take care of them before they translate into a painful breakdown. With long-term rentals, messages about a necessary maintenance can be sent automatically from the vehicle. When using the GPS option even theft warnings can be sent when the vehicle leaves a predefined area. The rental agency can observe the location of the vehicle on a computer at any time.
(This article has been published in CAN CiA’s News Letter.
CAN in Automation (CiA – www.can-cia.org) was formed in 1992 with a view to help promote, standardise and foster development in new applications of this innovative technology called CAN (Controller Area Network). CiA has appointed Global Technology in Mumbai to help CAN Community in India. Contact: Global Technology (CiA India Office). Email: info@globaltechnology.org.in]).
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