Application of 3D Hall Effect Sensors in Autonomous Mobile Robots

As the advanced manufacturing processes of Industry 4.0 sweep the global market, the demand for highly automated systems has increased dramatically. These systems need to operate in an integrated manufacturing process and continuously collect process control data. Most of these systems (including magnetic, actuator, linear motor and autonomous mobile robots in robotic arms) require advanced position sensing solutions to control performance and collect factory-level data to make more informed decisions and improve the safety and reliability of equipment operation.

The autonomous mobile robot shown can automatically perform simple tasks, such as transporting within a warehouse. This type of industrial robot can help optimize manufacturing processes, increase production volume, and improve productivity. To safely and efficiently navigate a factory floor or warehouse, the wheels of the autonomous mobile robot must have built-in high-precision system control functions such as position sensing and speed control.

High-performance automation systems that control motion almost all require position sensing, and the choice of position sensing technology directly affects the cost and performance of the entire system. When evaluating the best position sensing solutions, factors such as accuracy, speed, power, flexibility, and reliability need to be considered.

Multi-axis linear Hall effect sensors provide highly accurate, fast and reliable absolute position, ideal for precision automation industrial applications. These capabilities enable more accurate real-time control, which plays a vital role in improving equipment performance, optimizing system efficiency and minimizing downtime.

Looking back at the example of an autonomous mobile robot, the block diagram in Figure 2 shows the feedback loop formed between the wheels and the sensors. The TMAG5170 linear 3D Hall effect position sensor is used to monitor the exact angular position and rotation of the motor shaft, which in turn rotates the motor. In addition to all the elements shown in this feedback loop, the linear 3D Hall effect sensor will generally have a direct impact on the bandwidth and latency of the system. By using a sensor capable of high bandwidth measurements, you can increase the overall speed of this feedback loop and enhance system performance.

Likewise, the measurement accuracy of the position sensor determines how well the motor motion can be controlled. Often, there is a trade-off between sensor speed and accuracy, which limits system performance. The TMAG5170 enables high-throughput data readings with a sensing speed of up to 20 kSPS and high-precision linear measurements with a maximum total error of 2.6%, eliminating the need to choose between the two.

Figure: Block diagram of the wheel motor module for an autonomous mobile robot using the TMAG5170 linear 3D Hall effect position sensor

Power consumption can also be an important consideration when selecting a position sensor, depending on the management system or design. Battery-powered systems or systems with low-power power supplies (for example, remote 4 mA to 20 mA loop power) often require sensors with low-power operating modes (for example, wake-up and sleep and deep sleep modes) to help increase throughput while reducing power consumption. The TMAG5170 has multiple operating modes and sampling rates. Compared to other precision linear 3D Hall effect sensors, it has a power efficiency improvement of at least 70%, which can reduce power consumption in the 1 kHz to 20 kHz sampling range for battery-powered devices or light load modes where system efficiency is a concern.

Typically, position sensors have strict mechanical configuration constraints. Linear 3D Hall-effect sensors are feature-rich, with selectable magnetic sensitivity ranges and temperature compensation options, giving you flexibility in magnetic and mechanical design. The TMAG5170 features an on-chip angle calculation engine, eliminating the need for off-chip processing, while providing flexibility in the mechanical placement of the sensor and magnet in angle sensing applications, including on-axis and off-axis configurations.

As industrial systems work more closely with humans in automated operations, more safety measures are needed to ensure safe operation, and the demand for diagnostic features to prevent downtime and quality issues is increasing. When selecting a position sensor, in addition to factors such as accuracy, speed, power, and flexibility, reading reliability is also an important factor. For example, if a sensor with few or no diagnostic features is selected, a large number of external components may be required to ensure the accuracy and reliability of the sensor data, which will increase the bill of materials (BOM) cost of the design. The TMAG5170 has a unique combination of intelligent diagnostic features, such as communication, continuity and internal signal path checks, as well as diagnostic features that can be configured for power supply, input magnetic field, and system temperature. No additional components are required to ensure accurate sensor data, thereby achieving long-term reliability and reducing BOM costs.

High-speed and high-precision position sensors enable a new generation of real-time control technology in automated industrial systems. Precision linear 3D Hall effect sensors such as the TMAG5170 can help designers achieve fast, accurate and reliable measurements without sacrificing performance or increasing power consumption and cost, further promoting the development trend of the Industry 4.0 market.

Review editor: Tang Zihong