The responsibility to design a safe machine is heightened as demand on machine systems continues to expand and machines subsequently become more complex. To meet this market demand, equipment manufacturers and hydraulic suppliers are jointly using various risk analysis tools designed to highlight the "what if" scenarios associated with potential failures or malfunctions. EH controls are the ideal response to the complicated expectation of more productive machines with improved reliability and operational safety.

HSTs incorporating electrical pump control are especially suited for software and microprocessor control. A vehicle using some means of intelligent control can incorporate an infinite array of software algorithms that are designed to safely control and also monitor vehicle operation. HST acceleration and deceleration profiles are easily tuned to match desired requirements for safe vehicle operation.

Less obvious EH opportunities include self-diagnostics and system monitoring, such that if a failure were to occur it can be instantly detected and the machine placed in a fail-safe or de-energized state. Perhaps a limp home mode is desired if a particular fault is detected.

Beyond software
In addition to software control, integration of sensors and circuit valving is also becoming more accepted. Integrated or discrete sensors can be used to monitor pressure, speed, temperature, and pump displacement, so any number of safety-related circuits or controls can be achieved.

Integrated over-ride valves are rapidly becoming a system requirement where a vehicle can be held in a safe state until certain operator inputs are received. A vehicle can also be placed in a safe state when a fault is detected or an out-of-range output is recorded. The use of sensors and system monitoring, most importantly, enables the drive system to take preventive action prior to a disabling drive failure.

Pressure, speed, and temperature data logging for preventive maintenance or warranty administration are also easily provided with the capabilities of the onboard microprocessor intelligence and EH system monitoring.

Plug and perform
On-board EH intelligence in offroad HST machines plays a key role in improving drive performance and efficiency, as well as expanding vehicle capabilities and productivity. Additionally, an EH controlled HST can also shorten equipment assembly line and installation setup cycle times.

A smart controller can significantly reduce the setup time by eliminating the often time-consuming manual vehicle calibration and adjustment process of traditional mechanical or hydraulic pilot operated controls. An EH drive can quickly enter into a self calibrate mode where all thresholds and settings can be determined and stored in the controller memory. A secondary benefit exists within the aftermarket environment, where similar cycle time reductions can be found when a vehicle requires service or maintenance calibration.

Randy Rodgers and Branko Horvat are product managers, and Andy Sturtz and Darren Magner are application engineers for Sauer-Danfoss. Contact the company at 515-956-5750 or email Visit their web site at