Danaher - using wire-steering technology to improve forklift efficiency and safety
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To solve these problems, many forklift designers are considering converting their new forklifts to wire-steering steering systems, and some designers have already begun this conversion.
Characteristics of the steer-by-wire system The steer-by-wire system consists of an actuator and a driver. The electronic control system is used to increase the safety and efficiency of the forklift, such as cable guidance and stability. Therefore, the steer-by-wire system It offers special advantages for warehouse forklifts that are used for complex cargo handling in tight spaces. Since the power is only used when the steering system is working, the steer-by-wire system consumes less power; the hose is eliminated, reducing the weight, space, cost, and design flexibility of the steer-by-wire system. Significant improvements have been made. Electronically replacing hydraulics, when the forklift is moving in the opposite direction, it makes the steering wheel reverse action easier; the electronic stability control is added to ensure that the forklift does not go too fast when cornering. In the event of a failure of the steering system, the safety control system automatically stops the vehicle.
Steer-by-wire systems typically communicate via the industry standard CANOpen data communication protocol. With this protocol, various vehicle systems such as traction drives, brake-by-wire, shift-by-wire, and throttle-by-wire can be easily integrated. , to achieve perfect collaborative work, and run through a common control line, thereby reducing vehicle wiring costs and assembly costs. Controllers and brushless motors are usually integrated so that the space occupied by the steering system is greatly reduced.
In the forklift market, the transition to a steer-by-wire system coincides with the transition from a direct current (DC) motor to a permanent magnet (PMAC) motor. The advantage of PMAC motors is that they can achieve higher torques that are not possible with DC motors of the same size, with faster response and higher efficiency, enabling longer run times or using smaller batteries without real-time maintenance. . The efficiency of the PMAC motor is 85%, while the efficiency of the DC motor is only 65%. As a result, a typical steer-by-wire system consumes only 450 watts, while a typical hydraulic steering system consumes as much as 1.2 kW. In this way, the on-line steering forklift can increase the service life of the forklift battery by 3%-5%.
The steer-by-wire system is available for all major forklift types. A solution for counterbalanced forklift trucks with a load of 1 to 5.5 tons and a power of more than 5 kW has been developed.
Competitive Advantages Provided by Software One of the outstanding advantages of the wire-controlled steering system is the ability to provide special functions through software programming to increase the efficiency and safety of the forklift. For example, a steer-by-wire system can be integrated with a cable guidance system for safe operation of the forklift, while a wire is embedded in the ground and an audio current is applied to generate a magnetic field that can be detected by the cable guidance system on the forklift. The magnetic field is connected to the steer-by-wire system to control the forklift to travel straight along the centerline of the channel. This allows the truck to be transported in a warehouse with a slightly larger warehouse width than the forklift, saving space.
Since the steer-by-wire system does not require the driver to transmit mechanical force, it is possible to design a new steering method that can greatly improve ergonomics and improve driver productivity. An interesting example is the unrestricted 360 steering, where the driver can simply move backwards by changing the direction of the steering wheel. This feature significantly increases productivity in warehouses where operating space is limited. In general, the driver must first turn the steering wheel 90 degrees to the left and then 90 degrees to the right each time the cargo is loaded. With the 360 ​​steering feature, loading one load allows for fewer turns, so more pallets can be processed per hour.
Integrating this feature into a hydraulic steering system is costly and extremely complex, and can be easily implemented with a software-programmed, remote-controlled driving system that can be turned on with the push of a button. Or close.
Other unique functions can also be programmed via the steer-by-wire system. For example, a conventional 180° steering forklift can change the direction of the wheel when the forklift is reversely manipulated. This means that the forklift can move in the direction in which it is being turned when it is moving forward or backward.
Changing the steering sensitivity according to speed Using a steer-by-wire steering system, the steering wheel sensitivity can be changed depending on vehicle speed or other conditions. Generally, when programming the steering system, the vehicle has a higher steering sensitivity when moving slowly, and the sensitivity is greatly reduced when the vehicle speed is increased. This improves the work efficiency by allowing the driver to quickly turn the wheel when the vehicle is moving slowly, and reduces the steering ratio when the vehicle moves quickly.
It is worth noting that the steer-driving system itself does not provide tactile feedback, so some forklift manufacturers use a controllable force feedback device to generate torque feedback. Artificial force feedback often mimics the sensation of a conventional system being replaced. The controller is programmed by a haptic feedback algorithm that performs torque feedback modulation of the steering by a function of steering wheel rotational speed, acceleration, steering wheel position, rearward position, vehicle speed, or other parameters, and combinations thereof. More detailed information can be provided to the driver via a manual force feedback device rather than a conventional hydraulic steering system. For example, a pulsation when the vehicle is turning may indicate a vehicle failure; on the other hand, for some vehicles, such as a low speed picking vehicle, a simple friction device is sufficient.
Example of a line-controlled steering system The Hyster R30XM2 uses a line-controlled steering system to provide users with unique features. With steer-by-wire steering, the driver can steer the vehicle with a small wrist movement and comfortably drive the forklift in the direction of the fork shovel or frame, reducing work intensity. An optional cable guidance system can be integrated with the steer-by-wire system. With a steer-by-wire system, there is no need to provide a long hydraulic hose that is necessary to use the hydraulic steering method to move the hydraulic system up and down the driver's platform.
The Crown ESR4500 is another example of using wire-steering steering to maintain a competitive edge. This forklift provides 360 steering, and the driver can turn the truck in the opposite direction by turning the wheels in the opposite direction. With this system, the driver can choose to rotate 180 or 360 to match driving conditions, experience levels and personal preferences. Steering sensitivity decreases in proportion to the speed of travel, reducing the need for continuous correction. The result of the improvement is that the ESR4500 increases the number of pallets per hour by 18% and the energy consumption by 13% compared to similar forklifts.
Overall, steer-by-wire systems can reduce energy consumption, reduce component and assembly costs, and, more importantly, provide special features through software programming to increase productivity and safety. This is why the most innovative and technologically advanced forklift manufacturers are rapidly integrating this technology into the design of their new models.