With the rapid advancement of robotics technology, perception capabilities have become a core element driving the intelligence and multifunctionality of robots. Among the various sensors, Inertial Measurement Units (IMUs) and piezoelectric film sensors have gradually emerged as key technologies in the robotics field due to their unique performance and diverse application scenarios. IMUs, known for their precise measurement of attitude, motion, and direction, are widely used in navigation, control, and motion planning. Meanwhile, piezoelectric film sensors, with their high sensitivity, flexibility, and multifunctional characteristics, excel in areas such as tactile perception and vibration monitoring. This article explores the typical applications and future development directions of IMUs and piezoelectric film sensors in the robotics field, as well as the related solutions introduced by Murata.
Gyroscopes and accelerometers provide motion sensing capabilities for robots
The application and development of gyroscopes and accelerometers in intelligent robots are of great significance, as they provide robots with precise attitude control, navigation, and motion sensing capabilities. In terms of attitude control and stability, gyroscopes can measure a robot's angular velocity in three-dimensional space, helping maintain balance, which is particularly critical for bipedal robots and drones. Accelerometers, on the other hand, can monitor changes in linear acceleration during robot motion. When combined, they form an Inertial Measurement Unit (IMU), enabling precise attitude estimation.
Moreover, in GPS-denied environments, gyroscopes and accelerometers, through inertial navigation algorithms, can provide positional information, supporting autonomous movement in indoor or complex terrains. When integrated with vision sensors (such as SLAM technology), navigation accuracy is further enhanced. For collision detection and obstacle avoidance, accelerometers can detect abnormal acceleration changes during robot motion, enabling quick responses such as obstacle avoidance or halting actions.
In service and entertainment robot applications, these sensors can capture movements of the robot's arms or body to simulate human behavior or interact with users. Additionally, sensor data can be utilized to evaluate ground inclination, vibration, and dynamic changes in the external environment, enhancing the robot's adaptability to its surroundings.
Ultra-high precision 6-Axis MEMS inertial sensors
With the increasing functionality of industrial equipment, the number of electronic components incorporated is also continuously rising, necessitating sensor packaging miniaturization. Additionally, as the level of automation in industrial equipment continues to advance, the demand for accurately obtaining dynamic attitude angles and self-positioning information is also increasing.
Among these, the orthogonality of each axis (X-axis, Y-axis, and Z-axis) of the sensors is a critical factor for more precise estimation of dynamic attitude angles. To date, ensuring orthogonality has required users to perform external calibration through other devices.
To address this, Murata has developed high-precision 6-axis MEMS inertial sensors with low noise and stable output. Each axis of the gyroscope sensor and accelerometer sensor can output values with orthogonality compensation applied, simplifying the user calibration process and helping reduce production costs. Furthermore, the compact design aids in saving PCB space.
Murata’s SCH16T sensor series offers greater flexibility for customers through redundancy design options and built-in adjustable dual output channels. The SCH16T sensor series supports an angular rate measurement range of ±2000°/s (SCH16T-K10) or ±300°/s (SCH16T-K01), along with an acceleration measurement range of ±16g (SCH16T-K10) or ±8g (SCH16T-K01). It features an auxiliary digital accelerometer channel with a dynamic range of ±26g, gyroscope bias instability as low as 0.3°/h (SCH16T-K01) or 4°/h (SCH16T-K10), and noise density levels as low as 0.4m°/s/√Hz (SCH16T-K01) or 6m°/s/√Hz (SCH16T-K10). The sensors support interpolation and decimation options for synchronized data-ready output, timestamp indexing, and SYNC input functionality.
The SCH16T sensor series operates within a temperature range of −40 to 110°C, using a power supply voltage of 3.0 to 3.6V and I/O voltage of 1.7 to 3.6V. It supports the SafeSPI v2.0 interface and allows selection of 20-bit and 16-bit output data through SPI frames. With extensive self-diagnostic functions, its dimensions are 12mm × 14mm × 3mm (length × width × height), occupying a PCB footprint of less than 170mm². It features a robust SOIC plastic package compliant with RoHS standards, suitable for lead-free soldering processes and SMD mounting.
The SCH16T sensor is one of the few single-package 6DoF devices with this level of performance and functionality. It exhibits outstanding linearity and offset stability across the entire temperature and measurement range, achieving centimeter-level machine dynamics and position sensing accuracy even in harsh environments.
SCH16T is suitable for applications demanding high-performance operation under challenging environmental conditions, such as inertial measurement units (IMUs), inertial navigation and positioning, machine control and guidance, dynamic inclination, robot control, and drones (UAVs).
Murata also provides evaluation boards for the gyro/accelerometer combo sensors, SCH16T-K01-PCB and SCH16T-K10-PCB, which come pre-installed with SCH16T series sensors on a PCB equipped with passive components. The PCB facilitates SPI communication via pins.
Piezoelectric film sensors assist robots in sensing touch, pressing force, and vibration
Piezoelectric film sensors, with their characteristics of lightweight, high sensitivity, and rapid response, have broad application prospects and development potential in intelligent robots. In tactile sensing applications, piezoelectric film sensors can serve as flexible tactile sensors installed on the robot’s surface to detect external touch, pressing force, and vibration. These sensors help robots perceive the external environment and enable precise force control during object grasping and manipulation by accurately sensing contact forces.
Piezoelectric film sensors can also be used for vibration monitoring and fault detection. They monitor the vibrations of robot moving parts to detect early faults or anomalies, enabling preventive maintenance. Additionally, by detecting vibration features in the external environment, they enhance the robot’s adaptability to complex terrains and dynamic scenarios.
Ultra-thin and highly sensitive piezoelectric film sensors
Murata has utilized its proprietary piezoelectric technology to introduce the Picoleaf™ piezoelectric film sensor. This flexible, thin sensor is capable of highly sensitive detection of bending, twisting, pressing force, and vibration. It saves mounting space and achieves improvements in thinness, assembly performance, and durability compared to conventional sensors.
In addition, the piezoelectric film material used in Picoleaf™ is polylactic acid made by fermenting lactic acid extracted from plant tissue. Since plants absorb carbon dioxide from the atmosphere to synthesize starch, the material does not increase the total amount of carbon dioxide contributing to global warming. It is a carbon-neutral material that supports environmental sustainability.
Key features of the Picoleaf™ piezoelectric film sensor include adjustable amplification rate for output signals, customizable On/Off judgement threshold, and set filter configuration. It can control and monitor signals across up to four channels, and the GUI provides an intuitive overview of various settings and output status. Data can also be exported in CSV format.
With a thickness of 0.2mm or less, Picoleaf™ saves space even when combined with display or touch panel. Its compact dimensions of 2.5 × 7.0mm achieve ultra-small size. Picoleaf™’s flexible structure allows it to adhere to curved surfaces on highly designed devices, wrapped around cylindrical objects, and function in wet environments such as bathrooms or kitchens. It can detect pressing force underwater and be applied to water-using devices like washing machines. It is also capable of creating seamless buttons on metal casings.
The Picoleaf™ piezoelectric film sensor features high sensitivity, capable of detecting microscopic displacements as small as 1µm. A single sensor can detect pressing pressure across an entire display surface. Additionally, it can monitor biological signals such as involuntary muscle movements, gripping strength, and pulsation. The sensor is non-pyroelectric, eliminating drift caused by body temperature, sunlight, or semiconductor heat, thereby reducing noise induced by thermal effects.
Picoleaf™ exhibits low power consumption. The sensor itself consumes no power, and its driving amplification circuit can be designed for low current consumption (approximately 10µA). Furthermore, Picoleaf™ utilizes an environmentally friendly organic piezoelectric film made from plant-derived polylactic acid, contributing to sustainable development goals (SDGs) without increasing atmospheric CO2 during its lifecycle of manufacturing, disposal, and decomposition. It is also a lead-free product compliant with the European RoHS directive.
Picoleaf™ is suitable for applications involving pressing force detection. For example, it can function as a UI sensor leveraging its press-detection characteristics, be integrated into a stylus to detect hand grip states, and prevent unintended operations by detecting press actions. Moreover, Picoleaf™ is applicable for biological signal detection, such as monitoring pulsation and respiration, thanks to its high sensitivity.
Murata also offers evaluation boards equipped with GreenPAK™ programmable digital analyzer ICs produced by Renesas Electronics. These boards enable dynamic adjustment of output signal amplification rate and On/Off judgement threshold. With the ability to process signals from up to four channels simultaneously, the evaluation boards support multi-purpose assessments or assessments across multiple locations, improving evaluation speed and efficiency. Furthermore, the dedicated GUI facilitates intuitive parameter adjustments, as well as condition saving and sharing.
Conclusion
IMU and piezoelectric film sensors play an indispensable role in achieving precise motion control and flexible environmental perception in intelligent robots. These two types of sensors provide robust technical support for innovative applications in fields such as industrial automation, medical assistance, and service interaction. The gyroscopes, accelerometers, and piezoelectric film sensors launched by Murata are expected to help drive robotics technology toward higher levels of intelligence and diversification, enabling broader application development.