The SMX.igs-e inclination sensors from STW now feature inertial measurement unit (IMU) functionality and will enable sensor data fusion using Kalman filters in the future. The calculated values are passed on to subsequent control units via CAN, CANopen, or J1939.
Sensors have long since ceased to be pure data acquisition devices. Preprocessing of the acquired measurements is becoming more and more common in order to keep the amount of data on the machine network low and to reduce the processing load on the central control system. For these same reasons, Sensor-Technik Wiedemann (STW) has expanded the functional scope of its SMX.igs-e inclinometer and gyro-sensor family, the company explained. Typical applications of the sensors include determining the position of an excavator bucket, leveling machines and their attachments, and ensuring the stability of vehicles with extended booms.
The functionality of an IMU is now available. The accelerations and rotation rates in all three spatial axes are measured and output. Based on these measured values, one-dimensional or two-dimensional inclination values are calculated and output in 360° or ±90° ranges. The disturbances caused by dynamic influences or parasitic accelerations, such as movement, shock and vibration, which occur in all mobile applications, but especially in off-highway machines, influence the measurement results. To improve the stability of the calculated value in the presence of dynamic influences, various configurable filter algorithms are available to the user depending on the sensor type.
The user can select the settings and possible characteristics for the application from various filter types. In addition to the classic low-pass filters such as Butterworth and "critically damped", a sensor variant is now available in which includes a Kalman filter. This fuses the acceleration and rotation rate data. Based on this information, the returned values are calculated, and their further course estimated and corrected. The Kalman filter used is characterized by its dynamic range and yet damping of parasitic accelerations, explained the company. The attenuation is comparable to the classic low-pass filter, but the signal delay is almost negligible.
The calculated values are passed on to subsequent control units via CAN, CANopen, or J1939. The current version of the sensors allows configuration of the measuring range (±90° or 360°) and the choice of protocol. This represents flexibility in the design-in process, said the company. Commissioning is also intuitive, being supported with the STW software toolchain Opensyde. Preconfigured projects and dashboards in the software support integration of the sensor into existing and developed applications.
The SMX.igs-e is part of the company’s modular sensor family for mobile hydraulics. This family offers a product range for measuring and recording physical variables such as temperature, pressure, strain, inclination, and angular velocity. In mobile machines, the output values are used, among other things, to monitor and control the drive, the work function or energy management. They can also be made available on the Internet using onboard software and cloud solutions from STW, e.g. for predictive maintenance measures.
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