Designers Rediscover Potential of Electric Motors in Energy-Efficient Future

As is ever the case with engineering design, the primary trade-offs occur between power (energy), performance (efficiency), and area (miniaturization). While this is especially true in designing electronics like chips and boards, it is no less accurate in designing mechanical systems like motors, actuators, and gears. This article will focus on the latter—the unsung heroes of the electromechanical world. Let's start by clarifying a few misunderstandings in terminology before covering micro electric motor trends of energy efficiency, integration with smart technology, AI, and exciting applications.

First, what is the difference between motors and actuators? The terms are often interchangeable but have distinct meanings in engineering, particularly in mechanical and control systems. A motor is a device that converts electrical, hydraulic (fluid), pneumatic (air), or chemical (gasoline) energy into rotational or linear motion. Motors primarily generate raw motion or torque to drive mechanical systems. 

Conversely, an actuator takes energy from motors of all categories and converts the energy into mechanical motion to perform a specific function. More specifically, actuators control or move a component in response to a control signal. Motors are often components within actuators; for example, an electric motor might be part of a linear actuator that incorporates sensors, smart technology, and control systems (see Table 1).

Related:Parvalux Creates Optimal Motors with Rapid Prototyping

Key differences between motors and actuators

Table 1: Key differences between motors and actuators. JOHN BLYLER

The most implemented motor type in electromechanical systems are energy-efficient electric motors. From a global market perspective, the move toward such motor systems is driven by an industrial need to provide the same operational output while consuming less power. According to ResearchAndMarkets, the global market for electric motors is projected to grow from $187.6 billion in 2023 to $282.9 billion by 2030, reflecting a compound annual growth rate (CAGR) of 6.0%. 

Let's consider the trends in electric motor technology in more detail.

Motor trends

Many high-efficiency electric motor types are suitable for a wide range of applications. This article focuses on the micro electric direct-current (DC) motor category, which is popular in the design of medical devices, embedded IoT products, lightweight robots, and some energy systems. 

The more efficient DC motor is the brushless DC motor (BLDC). Without the need for brushes between the stator coils and rotor, brushless motors don't lose energy or speed to brushes, are quieter, and require less maintenance than brushed motors. 

Related:Meeting Medtech Motion Control Demands

One significant trend in many industries—from aerospace to manufacturing—is the replacement of traditional hydraulic- and pneumatic-based motor systems with micro electric versions. One advantage of these miniature motors is their high-power density, which allows for significant weight reduction as well as greater energy efficiency. 

"Replacing pneumatic systems with electric motors in manufacturing plants significantly enhances efficiency and sustainability while simultaneously reducing emissions," explains Adrien Mettraux, industry manager for aerospace and industrial markets at Portescap. "Electric motors are more energy-efficient, converting a higher percentage of electrical energy into mechanical work than pneumatic systems, which often suffer from energy losses due to air compression and leakage." (See Figure 1 below).    

Figure 1: These brushless DC slotted flat motors' miniature architectures and high power density make them a good choice for high-speed and peak-torque applications, such as power hand tools and electric grippers for robotics. PORTESCAP

Aside from removing energy losses associated with compressed air and related losses from cable leaks, micro electric motors are more efficient at converting electrical energy into mechanical work. The increased conversion efficiency results from such motors' electromagnetic (EM) interaction. The stator generates a magnetic field that interacts with the rotor or shaft, thus producing torque (see Figure 2). This process avoids many intermediate steps that can result in energy losses, unlike combustion engines, which require multiple steps to convert chemical energy into heat under pressure, resulting in mechanical work (motion).

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Figure 2: External view of electric motor stator and rotor.  PORTESCAP

Motor efficiency plays a critical role in battery-powered devices, especially ones used routinely throughout the workday, explains Dave Beckstoffer, senior industry manager at Portescap. He notes that increased efficiency is driven by new winding technologies, material advancements, and improved electromagnetic design, leading to lower losses during operation. This higher conversion of input power to output power enables smaller batteries to be utilized, reducing the device's architecture. 

Electric motors also generate less heat than pneumatic or combustion devices, so more of the input energy goes into creating motion. Fewer moving parts also help reduce friction, another source of lost energy. Fewer parts mean less wear on components, improving reliability and the motor's lifetime. 

A significant sustainability advantage of electric motors is the incorporation of sophisticated electronic controllers, which can optimize performance under varying conditions. These systems ensure the motor operates at or near its most efficient point.

Of course, electric motors have some drawbacks when replacing hydraulic or pneumatic motors. First, the initial up-front replacement cost can be higher than that of existing hydraulic or pneumatic components. However, long-term energy savings from the conversion often offset the initial cost. 

Electric motors may require additional design considerations for space and weight. However, micro electric motors are often the only viable implementation for miniaturized applications, e.g., consumer goods, robotic components, and medical devices. For more details, see "2 Ways Miniaturized Medical Motors Save Lives."

The power of piezo

Another micro electric DC motor type called piezoelectric motor uses ultrasonic energy. Unlike traditional electric motors, these devices produce motion through ultrasonic vibrations of a piezoelectric material subject to an electrical field. The piezoelectric effect occurs when certain materials (like quartz or ceramics) produce mechanical strain or deformation in response to an applied electrical voltage. When the core of a piezoelectric motor is deformed even slightly, motion can be created, thus eliminating the need for bulky and inefficient components such as gears and screws to convert rotation into linear motion.

Further, piezo motors convert electrical energy directly into mechanical motion without the intermediate steps that create inefficiencies in conventional motors, resulting in lower energy consumption. This high efficiency makes piezo motors particularly valuable in battery-sensitive systems, where extended operational life is critical.

"Piezoelectrics allows for much smaller and lighter motor designs, ideal for applications requiring compact packages, such as medical devices, micro-robotics, and aerospace technologies," notes Stefan Vorndran, VP of marketing at PI-USA. "Piezo motors not only save space but also improve energy efficiency, as they operate with minimal power loss—for example, their self-clamping properties allow them to hold a position without using energy, or the need of external brakes that require additional energy." (See Figure 3 below).

Figure 3: A compact linear motor based on piezoelectric materials. PI-USA)

A key consideration when using any micro electric motor in a new design or legacy application is how well it will integrate with the rest of the system.

Integration trends

Advances in sensors, embedded IoT connectivity, and robotic technologies have enabled real-time monitoring and optimization of motor performance. Careful hardware and software integration allows designers to enhance operational efficiency and support predictive maintenance, thus reducing downtime and extending motor life.

Today's intelligent motors and actuators incorporate embedded sensors to monitor temperature, vibration, torque, and speed. IoT connectivity ensures the sensor data is transmitted to edge networks and the cloud for data processing, monitoring, and diagnostics.

Real-time sensor data analysis is critical to detecting anomalies and pending failures, thus reducing downtime through predictive maintenance and support. For example, factories now use near real-time sensors, embedded processors, and edge-cloud computing to determine when motor bearings will fail on systems from production conveyor belts to critical medical devices. For more details, see "2 Tools to Avoid Costly System Maintenance and Unexpected Testing."

Machine learning (ML) algorithms can analyze motor data to optimize operation and adapt to changing load demands. This way, smart motors can adjust energy usage based on demand and improve sustainable operations with regional power sources.

Innovative motor technologies come at an initial price, but a justifiable return on investment (ROI) is achieved through energy savings and reduced maintenance costs. Another challenge faced by smart motors—due to connectivity to the Internet—is the risk of an attack by hackers. Still, that risk can be mitigated using secure communication protocols, for example, for industrial production systems based upon Modbus, EtherNet/IP, and Profinet.

Complexities will arise when new hardware and software are integrated into existing motor systems. For example, designers will have to adapt their traditional control systems to the different operating principles of electric motors. However, an integrated development team of electronic and mechanical engineers will make the process go more smoothly. 

Motors and AI

As mentioned, micro electric motors can use AI technologies like ML to optimize motor torque (the rotational force related to motion), predictive maintenance, and more. 

Optimizing torque is especially critical for the precision of micro electric motors used in medical devices and related robotics arms and grippers. Compact actuators used in small robotic arms require high-torque brushless DC motor control. Direct-drive motors are also being miniaturized to enable precise movements without complex gearing.

AI-based predictive maintenance (PdM) will optimize motor life and reduce downtime. Critical components of this approach require all of the smart motor technologies mentioned above, such as embedded sensor data collection and nearby data processing connectivity on an edge network of more robust processing on the cloud. 

Anomaly and fault detection need AI and machine learning models that use unsupervised learning to identify deviations from normal operating conditions. This approach may appear simple to implement, but the teaching must be tailored to each application, and training models must be designed to correctly label datasets to classify motor issues (e.g., misalignment, wear, overheating).

AI applications for micro electric motors are driving significant advancements in energy optimization, fault detection, and performance enhancement," confirms Mettraux of Portescap. "By leveraging AI algorithms, electric motors can operate at peak efficiency, dynamically adjusting to varying loads and conditions to minimize energy consumption. AI also enables real-time fault detection, continuously monitoring motor health and identifying potential issues before they lead to failures, reducing downtime and maintenance costs of electric systems. These capabilities improve the efficiency and reliability of micro electric motors and contribute to more sustainable and cost-effective operations across various industries."

High-tech motor applications abound

Smart and micro electric motors are finding homes in a growing number of applications. For example, robotic arms require motors that balance size, torque, and precision, which has led to innovations in compact actuators, soft robots, and collaborative robots (cobots). As noted above, compact actuators use direct drive motors to ensure precise movement and brushless DC motors are capable of very high torque motion, e.g., providing significant force output in a compact space for robotic lifting or pulling.

Soft robots use flexible, deformable mechanisms and actuators built with fluids and flexible materials, making them more suitable for exoskeletons or wearables. They are designed to mimic the mechanical properties of biological organisms, making them human-safe. New materials, like electroactive polymers and shape-memory alloys, are being explored for actuation in soft robotics. One example is the unique implementation of a robotic tail in "How to Build Your Own Robotic Tail."

Finally, cobots rely on miniaturized motors with embedded sensors to improve safety and precision when working in tight spaces beside human co-workers.

Other applications for micro electric motors are found in medical devices, consumer electrics such as wearables and smartphones, and aerospace drones. For the latter, the miniaturization of electronic and mechanical parts has led to a revolution in tiny unmanned aerial vehicles (UAV) or drones. For an example, see "Miniaturizing Technology for the Better."

Scaling down on the size of electric motors has been a key driver in all of these applications. Mechanical miniaturization has resulted in small actuators, gears, and motors—some so small they can easily fit inside the human body. 

Electric motors are a vital component in renewable energy systems thanks to their high energy efficiency in converting electrical energy into mechanical energy or vice versa and their miniaturized size, among other factors. Such motors are being used in solar energy systems and wind energy, just to name a few. 

Electric motors are needed to adjust the position of solar panels to optimize the amount of solar energy received. Motors are also required for inverters and converters, which convert the DC power generated by solar panels into alternating current (AC), which can be used by the electrical grid directly within solar-panel-equipped households. Again, the high efficiency of electric motors ensures that this conversion process is as efficient as possible, minimizing energy losses.

The wind turbine industry also relies heavily on electric motors, but here, the size of the motor needed depends on the turbine's size and the level of control required. Micro electric DC motors are generally used in smaller wind turbines due to ease of control and high efficiency at converting wind's kinetic energy into electricity. For larger wind turbines—the ones typically seen on mountain ridges—a larger electric AC motor is needed to handle the high wind loads, resulting in a higher power level required to feed existing power grids.

Future trends for electric motors look promising for several uses. For example, ultra-compact magnetically driven systems can replace traditional hardware gears. The advantages of the former are the elimination of frictional wear and tear due to contact, minimal noise and vibration, reduced maintenance needs, and the ability to operate in harsh environments without lubrication.

Motors themselves are becoming more customizable via additive manufacturing that enables industry-specific design without significant cost increases.

In the robotic and medical spaces, bio-inspired designs (soft robot) motors mimic biological mechanisms, like muscle fibers.

Designers of almost all kinds of smart and embedded systems will benefit from the innovation in micro (and macro) electric motor design.