Lighting, sensors and communications technologies are key enabling technologies for autonomous mobile robots (AMRs), allowing them to see, sense and interact with the real world. To achieve this, various types of sensors are employed, including temperature sensors, image sensors, LiDAR (for 3D mapping), rotational position sensors, and Visible Light Communication (VLC) sensors. This article will provide insights into considerations for AMR design and introduce solutions offered by onsemi in this field.
Assist AMR in environment perception and interaction
AMRs require the ability to perceive and monitor their environment and interact with it. Image sensors and image signal processors play a critical role in providing visual perception for AMRs, enabling them to navigate their surroundings and detect/recognize objects. Additionally, position sensors are used to measure the rotation of AMR wheels and other moving parts, enabling accurate tracking of their 3D position and orientation. Ultrasonic and infrared sensors are used to measure the distance to remote objects, allowing AMRs to detect obstacles and avoid collisions.
Lighting technologies such as LEDs enable AMRs to navigate, communicate, and operate in challenging environments. They can also be used to emit signals and indicate the robot's status or direction. When selecting lighting technology for AMRs, performance characteristics including brightness, color temperature, and power consumption need to be considered. LED controllers and drivers monitor the current flowing through LEDs and allow them to emit light of specific intensity and wavelength. LED driver circuits use high-side and low-side power MOSFETs to turn the LED current on and off, providing over-voltage and over-current protection while ensuring stability of the LED driver circuit.
Communication technology enables AMRs to transmit data and receive commands to other devices and systems. Parameters to consider when choosing AMR communication technology include its operating range, data rate, power consumption, and security. The operational range of communication must be sufficiently long to enable acceptable speed communication with other devices and systems in the surrounding environment. The transceiver’s power consumption must be kept low to extend battery life, and security is crucial to prevent corruption of AMR data and commands.
Bluetooth Low Energy (BLE) wireless communication technology is designed for low power consumption and is well-suited for battery-powered devices like AMRs. This protocol supports a range of data transfer rates used for transmitting sensor data and control signals between AMRs and other devices. BLE can also be used in indoor positioning systems, enabling AMRs to navigate in dynamic environments. On the other hand, Industrial Ethernet communication protocols provide real-time control and high-speed communication required for coordinating multiple AMRs.
Furthermore, the use of VLC technology allows AMRs to communicate securely with other devices and humans. Since the visible light spectrum ranges from 430 THz to 790 THz, VLC does not interfere with nearby wireless technologies like BLE, Zigbee, Ultra-Wideband (UWB), and Wi-Fi. Moreover, VLC is relatively more secure as it is inherently confined to line-of-sight transmission.
Innovative global shutter image sensor
The entire purpose of AMRs is to actively interact with the real world, and onsemi can support design engineers in selecting the best lighting, sensing, and connectivity solutions to achieve this goal.
onsemi offers a diverse range of image sensor choices, including both global shutter and rolling shutter image sensors. In the context of AMR applications, the AR0234CS image sensor from onsemi incorporates an innovative global shutter pixel design optimized for capturing moving scenes accurately and rapidly at a full resolution of 120 frames per second. This sensor produces clear and low-noise images in both low-light and bright scenarios.
The AR0234CS is a 2Mp CMOS digital image sensor with a 1/2.6-inch optical format and an active pixel array of 1920 (H) x 1200 (V). It includes advanced camera features such as automatic exposure control, windowing, row skip mode, column skip mode, pixel binning, and video and single-frame modes. It can be programmed through a simple two-wire serial interface. The AR0234CS boasts industry-leading global shutter efficiency, resulting in exceptionally sharp and clear digital images. Its ability to capture continuous video and single frames makes it an excellent choice for various applications including scanning, autonomous mobility, surveillance, and industrial quality control.
The AR0234CS features outstanding global shutter efficiency, characterized by low dark current/hot pixels, support for high linear full well, low operating power, small form factor, built-in statistical engine, and multiple functional modes including row and column skip modes, pixel binning, and more.
Position sensors that combine precision and speed
The NCS32100 from onsemi is an industrial rotary position sensor that combines accuracy and speed. With a 38mm sensor size, it offers ±50 arcsec accuracy at 6,000 RPM. For applications requiring lower accuracy, it supports speeds of up to 100,000 RPM. This new device utilizes a patented inductive position sensing method, making it highly suitable for industrial and robotic applications.
The NCS32100 provides a full-featured controller and sensor interface that, when used with printed circuit board sensors, enables high-resolution and high-accuracy angular sensing. It offers flexible configuration options, allowing it to connect to various inductive sensor patterns and providing various digital output formats. Inductive sensing technology has distinct advantages over traditional position sensor solutions and is applicable in scenarios including but not limited to temperature insensitivity, mechanical simplification, and insensitivity to contaminants.
The NCS32100 supports a 2.5MHz UART interface for connecting to half-duplex RS-485 drivers. It has a maximum speed at full accuracy of 6,000 RPM and a maximum functional rotor speed of 45,000 RPM. It operates within a power supply voltage range of 2.7V - 5.5V and supports battery backup for multi-turn count tracking. The sensor interface is highly configurable (up to 8 channels), and it reports internal device temperature through programmable over-temperature thresholds and reports backup battery voltage through programmable low-battery thresholds. The response time for external master data acquisition commands is as low as 3µs, and it operates at a full operation current of only 80mA. The sensor also supports self-calibration and features a 20-bit position resolution and 24-bit multi-turn resolution, along with a latency cancellation function.
LED drivers suitable for AMR lighting applications
onsemi's NVC7685 LED linear current driver and NCL31000 are intelligent LED drivers that are highly suitable for AMR lighting applications.
The NVC7685 supports 12 linear programmable constant current sources with a current of up to 60 mA, and allows for 128 different pulse width modulation (PWM) adjustable duty cycle levels. Each channel can have independent PWM duty cycle control through a PC and general PWM duty cycle control through I2C. The NVC7685 can be programmed via an I2C serial interface, and PWM frequency can be selected from four different configurations including 150, 300, 600, and 1200 Hz.
The NVC7685 can be used with microcontroller applications using the I2C bus or in standalone applications, with a choice between two different static configuration settings in standalone mode. The device also provides a 3.3 V voltage reference for applications with loads of up to 1 mA. The brightness levels of LEDs can be easily programmed using external resistors. Each channel has an internal circuit to detect open-load conditions with optional auto-recovery mode. If one driver is in an open-load state, other channels can be turned off based on programmable bits setting. The device is available in a compact SSOP24-EP package.
On the other hand, the NCL31000 is an intelligent LED driver designed for lighting applications. It uses visible light as a carrier and supports Visible Light Communication (VLC) and indoor positioning capabilities. It can transmit unidirectional data at speeds of up to 10 kb/s. The NCL31000 features an efficient 3A buck LED driver, high-bandwidth analog and PWM dimming (down to zero current), two auxiliary DC-DC converters for powering microcontrollers and other sensors, and diagnostic features for measuring input and output current and voltage, LED temperature, and DC-DC voltage.
The NCL31000 also integrates high-accuracy metrology (±1%) with a 3.3V buck converter, and an adjustable 2.5 to 24V buck converter. It supports I2C or SPI serial interfaces. The NCL31001 is a reduced functional version that allows for multi-channel solutions.
Low-power Bluetooth transceivers and industrial ethernet transceivers
onsemi's RSL15 is a Bluetooth 5.2 certified transceiver suitable for easy-to-implement low-power Bluetooth wireless applications. It supports Angle of Arrival (AoA) and Angle of Departure (AoD) key features for accurate indoor positioning. The highly integrated radio SoC optimizes system size and battery life.
RSL15 is a Bluetooth LE 5.2 wireless microcontroller (MCU) and custom protocol-based 2.4 GHz transceiver based on the ARM Cortex-M33 processor. It is designed for interconnected smart devices in industrial and medical applications. RSL15 features built-in power management, wide supply voltage range, flexible GPIO and clocking scheme, and extensive set of peripherals, offering maximum design flexibility for high-performance and ultra-low-power applications. RSL15 includes 80 kB of RAM and offers flash memory options of 284 kB or 512 kB. onsemi also offers the RSL15 Evaluation and Development Board (EVB), designed for use with the RSL15 Software Development Kit. It aims to evaluate the performance and features of RSL15 and developing, demonstrating, and debugging software applications for the device.
onsemi's NCN26010 is a 10BASE-T1S industrial Ethernet transceiver that enables multi-drop Ethernet communication for industrial applications using existing twisted-pair wire cabling. The device complies with the IEEE 802.3cg standard and includes a Media Access Controller (MAC), a PLCA Reconciliation Sublayer (RS), and a 10BASE-T1S PHY designed specifically for industrial multi-drop Ethernet. It provides all physical layer functions, transmitting and receiving data over a single unshielded twisted pair and can communicate with the host MCU using the Open Alliance MACPHY SPI protocol.
NCN26010 features Enhanced Noise Immunity (ENI), extending noise immunity well beyond the IEEE T1S standard, allowing the NCN26010 to withstand worst-case conditions for DPI and BCI noise immunity tests. When enabled, this significantly improves network coverage, nearly doubling that of competitors. The unique minimal line pin capacitance of NCN26010 allows for the maximum number of nodes per segment, supporting up to 40 nodes on a 25-meter segment, well above the IEEE minimum standard. This can lower costs associated with cabling, connectors, and installation.
Conclusion
With the maturation of sensing and positioning technologies, AMRs are becoming more capable of navigating complex environments, significantly enhancing their practicality and extending their applications and markets. onsemi offers essential image sensors, position sensors, lighting, and communication devices that meet the critical requirements of AMR design. onsemi also provides a complete set of development tools and technical support to accelerate AMR development, allowing customers to seize market opportunities.