In 1993, Daifuku developed the world's first monorail system that utilized a non-contact power supply*, which has garnered attention as the next-generation transport system to create a clean environment. The system supplies electric power to moving objects without coming into contact with them. The first system was delivered to the Iwate Plant of Kanto Auto Works, Ltd. in 1993 (photo). Since then, Daifuku's non-contact power supply transport systems have been expanding from the automobile industry to other industries, including semiconductors, food, and pharmaceuticals.
- *The noncontact power supply system was named HID, an acronym from High Efficiency Inductive Power Distribution Technology.
A Brief History of Development
The elementary technology of HID was invented in 1990 by a group of researchers at the University of Auckland, New Zealand, led by Professor John Boys. Daifuku conducted research and development jointly with the university and successfully put HID technology into practical use. Our HID technology solved drawbacks of the conventional contact power supply technology using trolley lines and collectors, including collector wear, wear debris, and sparks generated by line separation. Daifuku signed a technical license agreement with the University of Auckland and has the exclusive rights to the use and sale of HID in the material handling market. At present, the HID technology is patented in many countries.
Configuration and the Roles of Components of HID system
The HID system consists of the following four components.
HID Power Supply Panel
The power supply panel converts the commercial power supply to a frequency suited to noncontact power supply and feeds electric power to the induction cable.
The induction cable is a special electric line installed along the rail of a moving object. A magnetic field is generated around the cable in order to efficiently transmit electric power to a moving object.
The pickup coil is installed on the side of the moving object opposite the induction cable and receives electric power from the magnetic field around the induction cable.
Power Receiving Unit
The power receiving stabilizes electric power that the pickup coil receives and feeds quality electric power to inverters and servo drivers.
Features and Patents of the HID System
The features of the HID system are that the induction cable and the pickup coil are non-contact and that the induction cable is covered by insulating material. It has the following benefits.
(1) High reliability and durability
Collectors for non-contact power supply require a refined 3D mechanism in order to achieve stable contact. The HID has a simple structure and its noncontact configuration allows stable electric power supply for an extended period of time.
Conventional collectors may be increasingly worn out depending on the surrounding environment. Since the HID is non-contact, its collectors and trolley lines never become worn, and thus significantly reducing maintenance costs.
(3) Applicable to clean environments
The system never generates dust that contact collectors often produce. It is therefore indispensable for environments where no dust is allowed, such as clean rooms.
(4) Applicable to environments where oil mist and/or water vapor occurs
Contact power supply may not always be used in places where dust, oil mist, and/or water vapor occur. HID systems can be used in such places without problems.
(5) Safe power supply system
The power supply cable is entirely insulated and has no exposed parts, so there is no risk of electric shock. Electric power is supplied to the moving object by electromagnetic coupling and electric sparks will not be generated, making this is a very safe power supply system.
The idea for non-contact power supply can be found in a USA patent granted some 100 years ago. This technology is based on the accumulated knowledge of forerunners, including the law of electromagnetic induction. On the other hand, the development of simulation technology, the invention of elements which can be used in high frequency ranges, and advanced circuit technology were necessary to refine a non-contact power supply system to a practical level.
Since the tie-up with the University of Auckland, Daifuku has applied for tens of patents in major countries. The following are the core patents.
(1) Patent relating to the form of pickup coils and the configuration around induction cables
With the assumption that moving objects will travel in three dimensions, simulation was performed to determine the support of induction cables and the optimum form of pickup coils. As a result, the present E-shape core has been employed (Figure). This patent relates to the configuration that provides a good balance between power receiving efficiency and facility costs and is most suited to moving objects.
(2) Patent relating to power receiving units
The power receiving unit must supply stable power to control devices, such as inverters and sequencers, when the number of moving objects is changed or when electric power is changed at the moment of motor startup or the occurrence of regeneration. This patent relates to how efficiently and simply several kilowatt electric power can be controlled.
The HID system is widely used not only in the automobile, semiconductor, and flat panel display industries, but also in the optical fiber, food, and food container industries. In short, what many users want from their facilities is high availability. Specifically, this means that maintenance is unnecessary or minimal, only a short time is needed to change the facility's layout, errors and breakdowns do not occur, and recovery from problems is very quick. In addition, the mitigation of effects on the global environment and the provision of comfortable environments to human workers are significant concerns. We believe that our HID system will be broadly used in many industries as an important support technology to meet these requirements.
From DAIFUKU NEWS No.161 (August 2001)