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Views: 0 Author: Site Editor Publish Time: 2025-08-08 Origin: Site
In today’s world of automation, robotics, and precision engineering, resolvers remain one of the most trusted technologies for position and speed sensing. Although digital encoders have grown in popularity, resolvers continue to dominate in industries that demand robustness, reliability, and long-term performance under harsh operating conditions.
When selecting a resolver for your application, two of the most important factors to consider are speed and accuracy. These parameters directly affect how well the resolver integrates into your system, how reliably it operates under mechanical or electrical stress, and ultimately how efficiently your equipment performs.
This article will walk you through the fundamentals of resolver technology, the significance of speed and accuracy, and practical guidelines on how to select the right resolver for your application.
A resolver is an electromechanical transducer used to measure angular position and speed. It works on the principle of a rotating transformer:
The primary winding receives an AC excitation signal.
The secondary windings, typically arranged 90 degrees apart, generate signals proportional to the sine and cosine of the rotor’s angle.
By analyzing these signals, the system can determine the exact shaft position and rotational velocity.
Resolvers are valued for their ruggedness, resistance to extreme environments, and long operational life compared to other feedback devices like optical encoders. They are widely used in industrial automation, aerospace, electric vehicles, CNC machinery, and robotics.
Every application has unique demands. For example, a high-speed electric motor in an electric vehicle requires different feedback characteristics than a precision robotic arm or an aircraft control system.
Two primary performance metrics guide the selection of a resolver:
Speed Capability – The maximum shaft speed the resolver can track accurately.
Accuracy (or Angular Error) – The difference between the actual mechanical shaft angle and the electrical output angle.
Balancing these two is crucial: a resolver with high speed but poor accuracy may suit high-power industrial drives but fail in precise positioning tasks. Conversely, ultra-accurate resolvers may not withstand the high rotational stresses of heavy-duty motors.
Resolvers must be mechanically robust to handle high rotational speeds. The rotor, bearings, and shaft coupling must withstand centrifugal forces without generating excess vibration. Industrial-grade resolvers are typically rated for 10,000–20,000 RPM, while aerospace-grade versions may exceed this.
The excitation frequency (commonly 2–10 kHz) determines how well the resolver can track rapid changes in shaft position. Higher frequencies enable faster response but also demand more from the signal processing electronics.
Heat, vibration, and contamination (dust, oil, moisture) can all degrade performance at high speeds. Choosing a resolver with sealed housings and thermal resistance ensures reliable operation in extreme environments.
Accuracy depends heavily on the precision of winding placement and mechanical alignment. Small deviations can cause angular errors, usually measured in arc-minutes (1/60 of a degree). Standard industrial resolvers offer ±8–12 arc-minutes, while precision models may achieve ±2–4 arc-minutes.
Resolvers require demodulation circuits or resolver-to-digital converters (RDCs). The quality of these electronics directly influences accuracy. Noise, distortion, or poor analog-to-digital conversion can all increase angular error.
Resolver windings are subject to resistance changes under varying temperatures, which can shift output signals and affect accuracy. Choosing a resolver with temperature compensation helps maintain consistent performance.
Industrial systems such as pumps, compressors, fans, and conveyor drives typically operate at very high rotational speeds. In such cases, the priority is ensuring that the resolver can withstand continuous high-RPM operation without suffering from overheating or mechanical fatigue.
Speed Priority: Industrial motors often exceed thousands of revolutions per minute (RPM), meaning the resolver must reliably track fast shaft movements.
Accuracy Requirement: In most scenarios, extremely fine angular accuracy is not essential. A tolerance of around ±10 arc-minutes is usually sufficient to maintain smooth motor control and system efficiency.
Other Considerations: Since these environments often involve dust, moisture, and high ambient temperatures, the resolver should feature robust construction, sealed housings, and high thermal endurance.
Recommendation: Select a resolver designed for mechanical durability and thermal stability, ensuring long-term operation even under continuous heavy loads.
In robotic systems, automation lines, and CNC machinery, precision is the foundation of performance. A tiny positional error could result in defective products, inefficient motion paths, or even collisions between robotic arms.
Accuracy Priority: Robotic joints and CNC machine axes require extremely precise position feedback to execute complex movements with repeatability. Tolerances as tight as ±2–4 arc-minutes may be required.
Speed Requirement: Unlike industrial pumps or EV motors, robotic actuators typically operate at moderate speeds, making high-RPM durability less critical.
Other Considerations: Stability is just as important as accuracy. The resolver must maintain consistent output under varying mechanical loads and electrical interference.
Recommendation: Choose a resolver with tight accuracy tolerances, stable signal output, and noise immunity. Compact designs are often preferred in robotics due to limited installation space.
Balanced Priority: Flight control systems and radar platforms require both high accuracy and reliable speed tracking.
Recommendation: Use aerospace-grade resolvers designed for extreme conditions, with advanced shielding and thermal stability.
Speed Priority: EV traction motors spin at high RPM.
Accuracy Priority: Accurate enough to enable smooth torque control and regenerative braking.
Recommendation: Choose a resolver tested for automotive environments, balancing both speed and moderate accuracy.
Define Application Requirements
Maximum shaft speed (RPM)
Required angular accuracy
Environmental conditions (temperature, vibration, contaminants)
Consider Signal Processing Compatibility
Ensure the resolver matches your control system’s RDC specifications.
Higher excitation frequencies require compatible electronics.
Evaluate Durability and Reliability
Look for IP-rated protection if dust or fluids are present.
Consider shock and vibration resistance for heavy-duty applications.
Balance Cost and Performance
High-precision resolvers cost more.
Avoid overspecifying—choose only the accuracy and speed you truly need.
While encoders and digital sensors are growing, resolvers are not becoming obsolete. Instead, manufacturers are developing hybrid resolver systems with integrated electronics, offering both analog ruggedness and digital compatibility.
Resolvers are also being optimized for electric mobility, with compact, lightweight designs capable of handling the unique demands of traction motors.
As industries demand higher precision and reliability, resolvers will continue to play a vital role in bridging mechanical motion with electronic control.
Choosing the right resolver speed and accuracy depends on your application’s balance of mechanical demands, precision requirements, and environmental conditions. High-speed industrial drives prioritize durability, robotics requires precision, aerospace demands both, and automotive systems need a careful balance.
By understanding the trade-offs and matching specifications to your application, you can ensure long-term reliability and performance.
If you are exploring reliable resolver solutions for your business, consider connecting with NINGBO START MOTOR TECHNOLOGY Limited. With expertise in advanced motor technologies and motion control systems, they can provide tailored guidance to help you select the most suitable resolver for your needs.
