When it comes to integration of electronics, off-highway equipment lags behind automobiles. From a cost standpoint, the lower production volumes for off-highway vehicles have kept electronic hardware costs much higher than those used in automotive applications. Lacking a one-size fits all software, the cost of programming development and software licensing fees has also presented a significant barrier to more widespread use of electronics.
Laupretre Co.'s LKH vineyard tractor uses an electronically controlled hydrostatic drive that is easily configured to specific application requirements by the Laupretre personnel.
For small to mid-sized original equipment manufacturers (OEMs), and those supplying the rental equipment industry, skepticism remains regarding the feasibility of electronics. End users are concerned with introduction of technologies for which they are not equipped to provide service. OEMs fear a reliance on external suppliers for software development, especially considering that much of the performance differentiation of their vehicles depends on this software programming.
The do-it-yourself nature of Poclain Hydraulics' Easy Design software requires no programming skills whatsoever. A simple menu-driven program allows OEMs to choose their own combination of transmission functions to customize vehicle performance according to specific requirements.
Integration without intimidation
When Laupretre Co., Ige, France, began development for its new LKH vineyard tractor, designers knew exactly what they wanted: a new concept in hydrostatic transmissions. The transmission had to be automatic and easy to use, enabling the operator to concentrate on manipulating various tools or harvesting equipment in order to increase productivity and prevent fatigue. It needed to adapt to precise operations and joystick control with a constant speed function in the field. Transmission speed shifting needed to be transparent and undetectable to the operator. Other design objectives included quiet operation and features to reduce fuel consumption. Designers also wanted operators to be able to control the tractor much like an automobile when travelling on roads in going from one location to another.
More specifically, Laupretre designers wanted to incorporate control options, such as transmission horsepower limitation, that could be implemented over an entire range of multi-purpose tractor models. This meant the system would have to be programmable for specific applications, but not require having to learn special programming languages or routines. And it needed to be operational immediately.
Sèbastien Laupretre, president, revealed, "Poclain Hydraulics offered a ready-made electronic transmission control (SmartDrive Easy) that allowed us to launch the first prototype very quickly." In fact, Poclain's software simplified the set-up process, so Laupretre had the prototype machine up and running the same morning its SmartDrive Easy computer was installed.
Laying the groundwork
Each wheel of Laupretre's LKH vineyard tractor is driven by a hydraulic motor from Poclain Hydraulics. The motors are driven by a 55-cc/rev axial-piston pump from Sauer Danfoss and powered by a 100-hp Kubota engine. Motor operation features Twin Lock mode, a Poclain-patented configuration that connects the motors in series and parallel with the pump simultaneously. Twin Lock mode provides hydraulic traction control that automatically transfers torque from a slipping wheel to a tractive one with greater efficiency than standard series motor circuits.
In its work mode, the LKH can achieve speeds to 12 km/hr. Engine is speed controlled manually according to requirements of the work tools, with pump displacement controlled from a joystick. When precise positioning of the tractor is required, a pedal acts as an inching control by modifying the resolution of the joystick signal to the pump.
A switch shifts transmission operation to road mode, which is capable of speeds to 25 km/hr. Road mode allows using the joystick to control both engine speed and pump displacement simultaneously. In this mode, the motors operate at low-displacement to reduce the pump flow required to achieve maximum vehicle speed.
When higher torque is needed while in road mode, the motors automatically shift to full displacement. This may occur for driving the tractor in reverse or for hydrostatic braking, in which case the pedal that had been used for inching control in the work mode now acts as a brake pedal to control hydrostatic braking.
The versatile transmission control has provided substantial benefit for Laupretre's customers. Laupretre explained, "This is a new function for our customers. It reduces fuel consumption and noise when operating at lower speeds, which is important when travelling through populated areas." He revealed that some customers reduced fuel consumption by 20% when operating in road mode.
Laupretre also found the Smart-Drive Easy to be an economical solution. He added, "We looked at other electronic systems, but they included more capabilities than what we needed for our application.-Poclain Hydraulics has focused on the transmission, which perfectly addresses our needs."
These innovative features — including the SmartDrive Easy control — have differentiated the LKH tractor from the rest of the market. Laupr&Eth;tre says the innovations contributed to a 50% increase in sales for the company. He added, "We refer to the SmartDrive Easy as 'SDE'. To our customers, this has become as standard a reference as the term ABS."
Based on its success with the LKH, use of the SmartDrive Easy has been expanded to Laupretre's 3-wheel-drive model Teractive T1.
SmartDrive and other products from Poclain Hydraulics are available in North America from Poclain's headquarters in Sturtevant, Wis. For more information, visit www.poclain-hydraulics.com.
The SmartDrive Easy computer and PHASES Easy Design software work with most major brands of pumps, including electroproportional controlled versions from Poclain Hydraulics, Bosch Rexroth, Eaton Hydraulics, Linde, and Sauer-Danfoss. This provides a local distributor or OEM with flexibility in specifying transmission architecture.
The menu-driven PHASES Easy Design software directs users to complete all required programming for each desired function, with help screens to explain each step in the process. It prompts the user to enter information for a variety of control characteristics:
Acceleration and deceleration control — Vehicle responsiveness ( minimum and maximum speeds and acceleration and deceleration ramps) can be tailored to the application.
Infinitely variable speed — Through simultaneous control of both pump and motor displacement, the computer can provide an automatic transmission function and seamless shifting for smooth, infinitely variable speed proportional to operator input from a joystick or pedal. The result is smooth performance over a wide speed range using 2-, 3-, or 4-speed radial-piston motors.
Operating mode selection — This feature allows users to program distinctly different styles of operation for the same vehicle. This function can establish a work or field mode and a travel or road mode by creating different acceleration and deceleration ramps, or styles of transmission control and account for using different types of actuators, or activate or deactivate specific transmission functions for each mode.
Constant speed regulation — This feature typically is used as a cruise control in work mode to ensure constant vehicle speed for harvesting, chemical application, or other work operation.
Transmission power limitation — Available power from the engine often far exceeds the capacity of the transmission. When traveling between jobs, for example, excess power not being used by tools can overpower and damage the transmission. With horsepower limitation, the computer limits the power to the transmission to protect it.
Combined braking — The computer coordinates actuation of both mechanical and hydrostatic braking proportional to operator input to ensure that the hydrostatic transmission works with the mechanical braking system and not against it.
Automotive drive control — Typically used for travel mode, pump output is proportionately optimized with engine speed for a "drive-likeyourcar" feel that also reduces both fuel consumption and noise.
Anti-stall — The computer can monitor engine speed to keep it from stalling. Particularly appropriate in work mode, when horsepower demand causes a dramatic drop in engine speed, pump flow is reduced until power is once again available to resume normal operation.