When designing a bomb disposal robot for use in tight spaces like an airplane, subway car, or bus, where precise movement can be a matter of life or death, and every gram matters, the right servo drives can make all the difference. The Telemax bomb disposal robot was specially adapted for operations in narrow spaces, such as in aircraft, underground trains, and buses making the need for a compact servo drive an imperative.
Read this case study to learn about:
- How compact, high-power servo drives enable a bomb disposal robot to work efficiently in tight spaces, with hours of battery operation
- Getting up to 3.3 kW peak power using a matchbox-sized servo drive.
- Placing your drive almost anywhere on your machine.
- Minimizing your development time, resulting in a short time-to-market.
The entire vehicle could have a maximum weight of 80 kg, with the battery and motors accounting for most of the weight. The physical size of the robot and manipulator arm had to be kept as small as possible, since the manipulator is used in confined spaces. Other important considerations were:
- The 24 VDC battery supply requires drives that can support a high current.
- EtherCAT communication for fast, synchronized movement.
- High power-efficiency, enabling about two hours’ operating time on battery.
- Smooth movements of the manipulator.
- Highly controlled loop bandwidth.
The Elmo Motion Control Solution included:
Elmo’s Gold Whistle and Gold Tweeter servo drives were found to be the lightest, most-efficient and most-intelligent servo drives. Ultra-compact and lightweight, they were ideal for mounting within the joints of the robotic arm, enabling a modular, decentralized architecture and minimal wiring, with low EMI due to shorter motor wires. With a lot of onboard intelligence, they were found to be perfect for such a critical application.
Peak current just when it’s needed
Other advantages of the Elmo Motion Control servo drives are the generous peak current, which is twice the nominal current and is supplied over a period of three seconds. This function is useful when the manipulator needs to be “forced” beyond its rated range. After the three-second period, the drive reverts to the nominal current. Peak current is again available once the drive has sufficiently cooled down. This allows the user to finish the operation in a stepwise manner, without having to stop or switch off the manipulator.
High power-efficiency reduces manipulator weight and costs
The manipulator may be in use for up to two hours, which typically requires very large and bulky batteries. The high efficiency of the Elmo drives enables smaller and lighter-weight batteries, making the entire manipulator lighter and more efficient. Ultra-small and ultra-efficient, the Elmo drives are designed to be mounted on a PCB. They incorporate proprietary “Fast and Soft Switching Technology”, resulting in >99% efficiency yet negligible EMI. This enabled the use of a smaller actuator and eliminated the need for cooling fans and heatsinks, which further reduced the weight and product costs.
Advanced networking by EtherCAT
Elmo’s drives are controlled using standardized EtherCAT protocol. They have an advanced built-in tool for EtherCAT diagnostics, including a free run mode to monitor the EtherCAT network, as well as online read and write access to the EtherCAT slave CoE object dictionary and statistical EtherCAT data access.
Elmo’s Gold Whistle and Gold Tweeter servo drives can monitor and use the internal drive heatsink temperature via the user program. In addition to over-temperature switch-off protection, the drive can be programmed to send its actual heatsink temperature via the EtherCAT network to the controller. If allowed by the EtherCAT Master, the drive can autonomously reduce the maximum current on-the-fly and set an indicator flag.
Most limits can be changed on-the-fly while the motor is on, enabling the continuous operation needed for time-sensitive bomb disposal operations. Torque components of other axes that cause interference can be compensated for with a direct torque feed forward command via the EtherCAT network to the drive, independent of the actual operation mode.
Elmo has introduced new solutions and options since this bomb disposal robot was designed. Today:
- The system could be controlled and operated via Elmo’s Platinum Maestro (PMAS) multi-axis network controller, through a wireless network from a centralized PLC or computer.
- Using Elmo’s Platinum servo drives would add advanced functional safety features that are valuable for this robot since it works near people.
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