Realizing the Potential in Mechatronics

When SKF rolled out its concept "E-Truck" forklift, new possibilities were both imagined and realized from integrating mechanical and electronic technologies. Time has only accelerated interest in mechatronic solutions for off-highway vehicles.

Applications in the real world have moved forward. As an example, SKF has delivered an advanced mechatronic steering unit for Hamm AG's new series of DV tandem rollers. Hamm AG is one of the leading innovators in the field of compacting equipment for roads, airport runways, and bridges. The steer-by-wire unit is designed to improve the steering of the tandem roller machine and contribute to ergonomically comfortable working conditions for the driver.

Such a steer-by-wire module is only one of the "smart systems" engineered in the original all-electric concept forklift. Other key E-Truck components included electric actuators, which lift, tilt, and shift the mast and forks and tilt open the operator cab to expose the batteries; sensor bearings to communicate position, velocity, and acceleration feedback for the mast-height controller; and electric traction-motor wheels for propulsion, regenerative braking, and gearbox elimination.

Rolling out the all-electric E-Truck demonstrated how existing capabilities can eliminate hydraulics, reduce energy consumption, improve ergonomics for greater operator safety and comfort, and deliver new efficiencies and economies.

The concept was based largely on in-depth analysis of input from customers and end-users, who identified their needs for vehicle functionality and performance. Among OEMs, profitability remains top-of-mind.

OEMs continue to cite the need for products able to increase productivity and efficiency for end-users and promote product differentiation in the marketplace; perform reliably; and require simple maintenance. They confirm requirements for environmentally friendly products and express concerns about potential end-user exposure to hydraulic leaks or the exhaust of internal combustion engines. Operator safety (and the safety of surrounding workers) is paramount. And, in the quest to reduce manufacturing costs, OEMs strive toward more simplified and streamlined assembly procedures using fewer parts.

All these issues were addressed with the E-Truck concept, which began with a forklift truck stripped down to the frame. Existing systems were removed and the vehicle was rebuilt using an electromechanical steering system, actuators, mast height control, and direct-drive traction motors. Since then, many innovations incorporated into the concept forklift have found their way into OEM engineering departments and implemented for specific applications (such as the Hamm tandem rollers).

Among the more notable and available system and module technologies already brought to market are:

• Electro-hydraulic steering system. This combines the flexibility of electric steering with the power density of hydraulics. The system has its roots in the electromechanical model initially developed for the E-Truck.

The system factors out the steering column to enable more ergonomic steering solutions; reduce the number of parts; simplify assembly procedures and processes; and require less space. Without hydraulics in the steering column benefits can accrue in reduced noise; improved operator safety; decreased maintenance; and avoidance of hydraulic leaks.

The closed-loop system consists of a mechanical/electronic (mechatronic) steering module; a controller regulating all steering functions; kingpin bearing sensors featuring high resolution to achieve desired steering position input and actual steered wheel feedback; and electrically actuated proportional valve. Each component talks to the next using CAN-bus protocols.