Reducing NVH: A Guide to Improving Noise, Vibration and Harshness (NVH) In Low-Power Applications
Understanding NVH
Noise, Vibration and Harshness (NVH) are crucial considerations across various applications, from automobiles to desk fans. Typically, NVH is utilized as a common comfort metric in the automotive industry. This post explores the concept of NVH and its significance beyond the automotive industry. We will dive into the factors that contribute to noise and vibration in embedded applications and discuss effective solutions to enhance user comfort and prolong the lifespan of devices.
NVH encompasses noise, vibration and harshness. Noise refers to audible sounds, vibration refers to device oscillation and harshness combines noise and vibration to represent the overall user experience. By reducing noise and vibration, we can significantly improve user comfort.
Addressing Noise and Vibration in Small Devices
Small devices with moving parts, like fans and pumps, can significantly benefit from minimizing NVH. These devices find applications in various sectors, including electronic cooling, automotive cooling, industrial processes, personal cooling, plumbing and household appliances. Reducing NVH not only enhances the user experience but also prolongs the device's lifespan.
When it comes to motor control, several factors come into play, but two key elements are drive waveform and feedback control. The choice between trapezoidal and sinusoidal waveform generation depends on the application. Trapezoidal waveforms, while simpler, can achieve higher motor speeds but tend to be noisier and have torque ripples. In contrast, sinusoidal waveforms offer smoother and quieter motor operation with constant torque delivered to the motor but come with increased control complexity.
Another critical consideration in motor control is the choice of feedback signals between sensor and sensorless solutions. Sensor-based motor control excels in low-speed applications, offering precision by providing real-time feedback on rotor position. If sensor resolution is not important to the application, then Hall sensors are the less expensive option. For applications that need high resolution at high and low speeds, a quadrature sensor is a better pick. On the other hand, sensorless motor control is ideal for higher-speed applications, relying on the Back Electromagnetic Force (Back-EMF) signal to detect the zero cross and estimate the rotor position and speed, making it a cost-effective choice in certain scenarios.
In many cases, Brushless DC (BLDC) motors are preferred to tackle noise and vibration issues due to their ability to deliver smooth operation, especially Permanent Magnet Synchronous Motor (PMSM) brushless motors. However, achieving this smoothness often demands advanced control techniques, which might necessitate high-end control devices. Most 8-bit microcontrollers (MCUs) on the market struggle to generate near-sinusoidal waveforms and ensure sensorless control.
We offer a cost-effective solution for controlling BLDC motors, particularly in low-power applications. The AVR® EB Microcontroller (MCU) provides smoother motor operation and enhances the longevity of system components.
Introducing the AVR® EB MCU
The AVR EB MCU offers an effective and cost-efficient solution for addressing NVH in low-power applications. Equipped with the latest Core Independent Peripherals (CIPs), the AVR EB MCU improves both NVH and energy efficiency. One noteworthy CIP is the Timer Counter E (TCE) with Waveform Extension (WEX), designed to provide smoother BLDC motor control and high-accuracy frequency generation. Additionally, the MCU incorporates other advanced features, including the Event System, introduced to help with inter-peripheral signaling design flexibility, Configurable Custom Cell (CCL) to automate task handling in your system, Analog Comparators (AC) for protections and fast feedback acquisition and a 12-bit Analog-to-Digital Converter (ADC) with internal Programmable Gain Amplifier (PGA) for precise analog signal acquisition. All these CIPs and more help reduce code complexity and overall Bill of Materials (BOM) cost. For safety critical applications, such as industrial and automotive products, a suite of functional safety tools and documents is available.
For low power, you have three sleep modes: idle with all peripherals running for immediate wake-up, standby with a configurable operation of selected peripherals and power-down with full data retention.
The AVR EB MCU can run up to 20 MHz with 32 KB Flash with dedicated Read-While-Write (RWW) section, 3 KB SRAM and 512B of EEPROM in 32-pin VQFN and TQFP packages. It has a supply voltage range of 1.8–5.5V and can withstand extreme conditions operating at temperatures from −40°C to 125°C, ensuring reliable performance even in challenging environments.
The new peripherals are combined with an innovative algorithm to implement a sinusoidal drive for BLDC motors with BEMF feedback control for sensorless motors, thus gaining the best of both worlds: simple control and optimized drive for NVH.
Streamlined Development Design
Developing with the AVR EB MCU is made easier through pre-made drivers and application code examples, which are freely available for use. Additionally, the MPLAB® X integrated development platform and the user-friendly MPLAB® Code Configurator (MCC) simplify peripheral configuration and tailor functions specific to your application. These tools allow for seamless transformation of innovative ideas into market-ready solutions.
Getting Started
Start reducing noise and vibration in your application by prototyping with the AVR EB Curiosity Nano Development Board, with the included TCE and WEX peripherals for cost-effective and low-power motor control. Along with the development board, MPLAB® X Integrated Development Environment (IDE) and MCC streamline the design process and enable you to bring innovative solutions to market swiftly and effectively.
