Autonomous Mobile Robots (AMRs) have brought numerous advantages to various fields and industries, including improved safety and efficiency. However, to enable AMRs to work safely and independently, these complex systems require careful integration of multiple technologies, with power and motion control being two crucial components. This article will provide you with design considerations for AMRs and the corresponding solutions offered by onsemi.
The power and motor control subsystems of AMRs play a crucial role
AMRs, having performance similar to self-driving cars, are complex designs consisting of a series of subsystems. These robots are capable of moving, observing, and operating safely with minimal human interaction. To create a flexible and intelligent AMR, the role of power and motion control technology is crucial. Over time, the choice of individual systems and components can significantly impact the performance and reliability of these advanced solutions.
Firstly, the power systems and components used in AMRs have a significant impact on their overall battery life and operating duration. When designing a power system for an AMR, factors such as energy density, voltage and current requirements, efficiency, solution size, and other important performance characteristics and parameters need to be considered.
AMRs commonly use lithium-ion batteries due to their high energy density and long runtimes. The power management unit regulates the flow of power from the battery to other components. Voltage and current levels are controlled using switching converters and regulators. The battery management system in AMRs monitors the battery's state, charge level, temperature, and current to ensure the AMR operates safely and efficiently, while the specifications of the onboard battery charger depend on the battery type, capacity, and voltage. Intelligent power modules provide high-power switching for the motor control system, and power switches in IPMs are equipped with gate drivers to provide the necessary signals to turn on and off the switches. Power factor correction (PFC) controllers can improve the overall efficiency of the power system.
Secondly, in AMRs, motor-driven actuators are used for moving robotic arms and wheels, making their selection crucial. High-torque and high-speed actuators that are efficient, compact, and lightweight are required for AMRs. When choosing actuators, a review of components such as brushless DC (BLDC) motors, motor controllers, MOSFETs, Universal Controller Boards (UCB), and gate drivers is essential.
Compared to brushed motors, BLDC motors have several advantages. BLDC motors are highly efficient, low noise, and highly reliable, reducing maintenance work, and are, therefore, widely used in AMRs. However, controlling such motors requires complex algorithms and appropriate drivers, with three-phase BLDC motors being commonly used in robots and industrial drives.
Motor controllers are responsible for precisely controlling the motors in AMR actuators. These devices can be fully integrated by embedding control algorithms or using dedicated microcontroller unit (MCU) to run motor control algorithms. Common three-phase motors in AMRs are driven using pulse-width modulated (PWM) ON-OFF signals by power transistors. These switches can be made of silicon or wide-bandgap materials such as silicon carbide (SiC) or gallium nitride (GaN).
Reliable intelligent power and motor control solutions
onsemi provides a wide range of reliable intelligent power, motor control, and sensing solutions, simplifying the complexity of designs and offering a solid foundation for their customers. These subsystem solutions are built on onsemi's decades of experience and technological expertise in the automotive industry, spanning from robust, high-resolution imaging systems to high-power motor control and efficient, compact battery charging solutions. onsemi's series of solutions streamline the development process, ensuring that AMRs can quickly adapt and operate reliably even in the most demanding work environments.
For power supply applications, onsemi offers a variety of Power Factor Correction (PFC) controllers that are well-suited for AC-DC power supply applications. These controllers can be used in applications like Totem Pole Bridgeless PFC front ends or DC-DC stages based on LLC resonant topologies. They are also suitable for high-voltage DC-DC power stages, making them ideal for designing high-efficiency and high-density fast battery chargers for AMRs.
In the BLDC motor control solutions, onsemi offers a range of components, including the ECS640A ecoSpin™ Motor Control UCB, the NCP81075 gate driver, and power boards that can accelerate the development of AMR actuators.
UCB is a system-on-module (SoM) based on Xilinx® Zynq®-7000 SoC, well-suited for precision applications and can also be used for advanced artificial intelligence (AI). In addition, onsemi provides MOSFETs based on shielded gate trench technology in the range of 30V to 150V, along with package options like u8FL, SO8-FL, dual cooling, and top-sided cooling.
The new 30-40V and 80V MOSFETs based on T10 technology are designed to support both low-voltage and medium-voltage applications. T10 devices are categorized into two main types, one for power conversion and the other for motor control. The T10M devices intended for motor control applications offer best in class on-state resistance, a 10% improvement in UIS capability, and outstanding body diode softness recovery performance. These features can help reduce voltage spikes and address EMI issues in motor control applications.
For high-power applications involving three-phase BLDC motors, onsemi recommends using MOSFETs based on PTNG technology with voltage ratings of 80V, 100V, 120V, and 150V. Additionally, NTMTSC1D6N10MC, NTMTSC4D3N15MC, NTBLS1D5N10MC, and NTBLS4D3N15MC MOSFETs are suitable for meeting the requirements of high-performance applications.
Highly integrated low-power three-phase BLDC motor controller
onsemi's ECS640A is the latest addition to the ecoSpin™ configurable motor control series. It is a three-phase BLDC motor controller that integrates an ultra-low-power-optimized Arm Cortex-M0+ microcontroller, three current sensing amplifiers, a reference amplifier (NCS20034), three bootstrap diodes, and a high-voltage gate driver designed for high-voltage and high-speed operation capable of driving MOSFETs and IGBTs up to 600V (FAN73896).
The ECS640A provides six gate driver outputs that supply 350 mA/650 mA (typical) gate current for external power devices. The device includes Hall sensor inputs, supporting sensored or sensorless operation, and three independent low-side source pin configurations that enable single or multiple current shunt measurements. ECS640A's protection features include undervoltage lockout and inverter overcurrent shutdown, with an automatic fault-clear function. It also provides an open-drain fault signal to indicate a fault condition.
The ECS640A now features Direct Torque and Flux Control (DTFC) firmware, which allows for optimal motor performance on the Arm Cortex-M0+ platform. Customers can obtain the DTFC code license directly from Theta Power Systems, Intl. The ECS640A's small footprint and high level of integration make it well-suited for discrete power devices, maximizing cross-platform scalability and minimizing space requirements as power levels expand.
The ECS640A features an embedded Arm Cortex-M0+ microcontroller with 64 kB of flash memory and 8 kB of SRAM support. It also supports the 600V FAN73896 gate driver and the NCS20034, a 7 MHz, high slew-rate, rail-to-rail quad amplifier, all housed in a small footprint SiP and includes a user-friendly environment for ease of use.
The ECS640A is commonly used in applications such as refrigeration compressors and blowers, HVAC blowers and condensers, pool pumps, industrial drives, pumps, and robotics. Common end products that utilize the ECS640A include refrigerators, bottle coolers, consumer A/C units, HVAC blowers, commercial A/C units, white goods, and coBots, among others.
High-performance dual MOSFET gate driver
The NCP81075 is a high-performance dual MOSFET gate driver introduced by onsemi. It is optimized to drive the gate of high-side and low-side power MOSFETs in synchronous buck converters. The NCP81075 integrates a gate driver IC and a bootstrap diode on-chip, eliminating the need for external discrete diodes. It has a high drive capability of up to 4A, making it suitable for driving high-speed, high-voltage MOSFETs operating at voltages up to 180V. The high-side and low-side drivers can be independently controlled, and they feature matched turn-on and turn-off propagation delays of 4 ns typical, with matched 3.5 ns typical propagation delay.
The NCP81075 is capable of driving two N-channel MOSFETs, one on the high side and the other on the low side. It integrates an internal bootstrap diode, allowing for a bootstrap voltage supply of up to 180V. This gate driver can operate at high switching frequencies of up to 1 MHz. It has a pull-up current capability of 4A and a pull-down current capability of 4A, making it suitable for driving fast switching applications. It can drive 1nF loads with typical rise and fall times of 8ns and 7ns, respectively. The NCP81075 operates over a wide supply voltage range of 8.5V to 20V.
Additionally, the NCP81075 features fast propagation delay times with a typical value of 20ns and a matching delay of 2ns (typical). It has a wide operating temperature range of -40°C to 140°C, making it suitable for a variety of environments. The device includes an Under-Voltage Lockout (UVLO) protection feature, which forces the output low when the driving voltage falls below a specific threshold. This UVLO protection helps ensure safe and reliable operation.
The NCP81075 is available in SOIC-8 (D), DFN8 (MN), and WDFN10 (MT) packages. These devices are Pb-free, halogen-free/BFR-free, and compliant with RoHS standards. They find wide applications in telecommunications, data communications, high-voltage buck converters, isolated power supplies, Class D audio amplifiers, dual-switch, and active clamp forward converters. The NCP81075 is also suitable for use in solar optimizer and solar inverter applications.
Conclusion
The application of AMRs continues to grow in various industries. However, the success of AMR applications relies on the integration of various technologies to ensure they operate autonomously, reliably, and safely. Choosing the right technologies during the design phase is crucial. onsemi can provide not only power and motor control solutions but also a wide range of sensors (such as image, temperature, LiDAR, rotational motion, visible light communication), as well as solutions for lighting and communication. This comprehensive product offering ensures that AMRs can reach their full potential, making onsemi an ideal partner for engineers developing AMR applications.