In the rapidly evolving field of industrial automation and robotics, the demand for high-performance actuation systems has never been greater. As AI robots become increasingly integral to manufacturing, logistics, and service applications, the need for compact, efficient, and precise electric actuators has emerged as a critical factor in achieving optimal performance. This article presents a detailed exploration of a compact electric actuator designed specifically for AI robot applications, focusing on its innovative structure, performance characteristics, and environmental adaptability. The actuator incorporates a frameless torque motor, planetary roller screw, and advanced control systems to deliver high thrust and precision in a minimal footprint, making it ideal for integration into AI robot joints and end-effectors where space and weight constraints are paramount.
The design philosophy centers on spatial multiplexing, where components are arranged to share physical space, thereby reducing overall dimensions and weight. This approach is essential for AI robots, which often require multiple actuators for complex movements without compromising agility or power. By leveraging direct drive principles and domestic components, this actuator achieves a rated thrust of 3.5 kN over a 22 mm stroke, with a maximum speed of 25 mm/s, all while operating reliably in temperatures from -40°C to 85°C. Through this work, we aim to provide a technical reference for developing similar high-performance actuators that meet the stringent demands of AI robot systems.
Introduction to Actuation in AI Robots
Electric actuators are fundamental to the functionality of AI robots, enabling precise control of movements in tasks such as object manipulation, navigation, and interaction with environments. Unlike traditional industrial applications, AI robots demand actuators that are not only powerful but also lightweight, responsive, and capable of operating in diverse conditions. The compact electric actuator described here addresses these needs by integrating a frameless torque motor, planetary roller screw, electromagnetic brake, and a high-resolution encoder. This combination ensures minimal backlash, high repeatability, and rapid response times, which are crucial for AI robots performing delicate operations or dynamic tasks.
In recent years, the proliferation of AI robots in sectors like healthcare, automotive assembly, and domestic services has driven innovation in actuator technology. However, many existing solutions rely on imported components, leading to supply chain vulnerabilities and higher costs. Our design emphasizes localization, using domestically sourced parts to enhance sustainability and reduce dependencies. By focusing on spatial reuse and direct drive mechanisms, this actuator achieves a 30% reduction in size and weight compared to conventional models, making it a viable option for next-generation AI robots. This article delves into the working principles, structural design, and performance metrics, highlighting how this actuator can revolutionize AI robot applications.
Technical Requirements for AI Robot Actuators
To ensure compatibility with AI robot systems, the actuator must meet specific technical criteria. These requirements are derived from real-world scenarios where AI robots handle payloads, navigate uneven terrain, or execute precise maneuvers. The following specifications were established as design targets:
| Parameter | Value |
|---|---|
| Effective Stroke | ≥ 22 mm |
| Rated Thrust | ≥ 3 kN |
| Rated Speed | ≥ 22 mm/s |
| Braking System | Electromagnetic brake with multi-turn absolute encoder |
| Positioning Accuracy | ≤ 0.2 mm |
| Locking Mechanism | Position lock via motor brake at any point |
| Structural Features | Compact, low inertia, fast response |
| Noise Level | ≤ 80 dB at 1 m distance |
These requirements ensure that the actuator can support AI robots in tasks requiring high force output, smooth motion, and minimal acoustic disturbance. For instance, in collaborative AI robots working alongside humans, low noise and precise control are essential for safety and efficiency. The inclusion of a braking system and encoder further enhances reliability, allowing the actuator to maintain position under load and provide feedback for closed-loop control.
Technical Design and Component Selection
The actuator’s design revolves around a core assembly comprising a frameless torque motor, planetary roller screw, cylinder, electromagnetic brake, and encoder. This integrated approach eliminates the need for additional transmission elements, reducing complexity and improving efficiency. Below, we break down the key components and their roles in the context of AI robot applications.
Frameless Torque Motor
The frameless torque motor serves as the primary drive unit, offering high torque density and direct coupling to the load. Unlike conventional motors, it lacks a housing and bearings, allowing it to be embedded directly into the actuator structure. This design reduces inertia and enables faster response times, which is critical for AI robots that require rapid adjustments in motion. The motor operates on the principle of electromagnetic field interaction, where the stator windings generate a rotating magnetic field that drives the rotor’s permanent magnets. The torque output is proportional to the current input, as described by the equation:
$$ T = k_t \cdot I $$
where \( T \) is the torque in N·m, \( k_t \) is the torque constant, and \( I \) is the current in A. For AI robots, this direct drive approach minimizes backlash and improves positioning accuracy, contributing to smoother and more predictable movements.
The motor selected for this actuator has a rated torque of 1.4 N·m and a peak current of 16.7 A, ensuring sufficient power for high-thrust applications. Its frameless design also facilitates better heat dissipation, as the windings are in direct contact with the actuator housing, reducing thermal rise and enhancing longevity. This is particularly important for AI robots operating in confined spaces or under continuous use, where overheating could lead to performance degradation.
Planetary Roller Screw Mechanism
The planetary roller screw converts the motor’s rotational motion into linear displacement, providing high efficiency and load capacity. This mechanism consists of a screw shaft, nut, and multiple rollers that distribute load evenly, reducing wear and increasing lifespan. The lead of the screw is 1 mm, which, combined with the motor’s speed, determines the actuator’s linear velocity. The conversion efficiency can be expressed as:
$$ \eta = \frac{F \cdot L}{2 \pi \cdot T} $$
where \( F \) is the thrust force in kN, \( L \) is the lead in mm, \( T \) is the torque in N·m, and \( \eta \) is the efficiency. For this design, the overall efficiency is approximately 0.8, accounting for losses in bearings and the screw assembly. This high efficiency is vital for AI robots, as it minimizes energy consumption and heat generation, extending operational time in battery-powered applications.
The roller screw is made from 42CrMo alloy steel, heat-treated to achieve a hardness of HRC 28-32, and precision-ground to ensure smooth operation. The nut uses wear-resistant bronze (ZCuSn10P), which reduces friction and maintains performance over long periods. By eliminating traditional gearing, this direct drive setup achieves a backlash of less than 0.01 mm, enabling precise control essential for AI robots performing tasks like assembly or surgery.
Electromagnetic Brake and Encoder System
Safety and precision are paramount in AI robot systems, necessitating reliable braking and feedback mechanisms. The electromagnetic brake engages within milliseconds to lock the actuator in position, preventing unintended movement during power loss or emergencies. It operates on a dual-mode system, combining electromagnetic and mechanical elements for redundancy. The brake force can be calculated using:
$$ F_b = \mu \cdot N $$
where \( F_b \) is the braking force, \( \mu \) is the friction coefficient, and \( N \) is the normal force applied by the brake pads. This ensures that the actuator can hold its position under the full rated thrust of 3.5 kN, a key requirement for AI robots handling heavy payloads.
Complementing the brake, a 23-bit multi-turn absolute encoder provides real-time position feedback. This encoder has a resolution of \( 2^{23} \) counts per revolution, allowing for sub-millimeter accuracy in positioning. The feedback loop enables closed-loop control, where the actuator continuously adjusts its position based on input signals. For AI robots, this means improved trajectory tracking and error correction, enhancing overall system intelligence and autonomy.
Parameter Analysis and Sizing
To meet the technical requirements, a detailed parameter analysis was conducted. This involved calculating the necessary motor torque, speed, and screw parameters to achieve the desired thrust and velocity. The following equations guided the selection process:
For thrust calculation:
$$ F = \frac{2 \pi \cdot T \cdot \eta}{L} $$
where \( F \) is the thrust in kN, \( T \) is the motor torque in N·m, \( \eta \) is the efficiency (0.8), and \( L \) is the screw lead (1 mm). Substituting the motor’s rated torque of 1.4 N·m:
$$ F = \frac{2 \pi \cdot 1.4 \cdot 0.8}{0.001} = 3.5 \, \text{kN} $$
This confirms that the actuator meets the rated thrust requirement of 3 kN. For speed, the linear velocity is derived from the motor speed and screw lead:
$$ V = \frac{N \cdot L}{60} $$
where \( V \) is the velocity in mm/s, \( N \) is the motor speed in rpm, and \( L \) is the lead in mm. With a motor rated at 1500 rpm:
$$ V = \frac{1500 \cdot 1}{60} = 25 \, \text{mm/s} $$
This exceeds the minimum speed requirement of 22 mm/s. The motor parameters are summarized in the table below:
| Motor Parameter | Value |
|---|---|
| Rated Voltage | DC 28 V |
| Pole Number | 14 |
| Rated Power | 110 W |
| Rated Speed | 1500 rpm |
| Rated Torque | 1.4 N·m |
| Peak Current | 16.7 A (RMS) |
| Back EMF | 6.2 V/k·min⁻¹ |
| Insulation Class | F (155°C) |
| Weight | 1.4 kg |
These parameters ensure that the actuator can deliver consistent performance for AI robots, even under varying loads and environmental conditions. The use of domestic components further enhances reliability and reduces lead times, supporting the scalability of AI robot deployments.
Compact Electric Actuator Parameters
The overall specifications of the actuator are listed in the following table, highlighting its suitability for AI robot integration. These values were validated through prototyping and testing, confirming compliance with the initial requirements.
| Actuator Parameter | Value |
|---|---|
| Effective Stroke | 22 mm |
| Screw Lead | 8 × 1 mm |
| Rated Thrust | 3.5 kN |
| Rated Speed | 25 mm/s |
| Motor Power | 110 W |
| Motor Rated Speed | 1500 rpm |
| Encoder Type | Multi-turn Absolute |
| Anti-rotation Mechanism | Integrated |
| Weight | 1.4 kg |
| Positioning Accuracy | 0.5 mm |
| Temperature Range | -55°C to +75°C |
| Mounting Style | Front Flange |
These parameters demonstrate the actuator’s ability to perform in harsh environments, such as those encountered by AI robots in outdoor or industrial settings. The compact design and low weight make it easy to integrate into multi-joint systems, enabling complex kinematics without excessive bulk.
Overall Structural Design
The actuator’s structure is optimized for spatial multiplexing, where components like the frameless motor, encoder, and brake are arranged concentrically to minimize length and diameter. This is achieved by using a hollow shaft design, allowing the screw to pass through the motor’s center and utilize the internal space of the encoder disc, brake seat, and locking nut. As a result, the actuator achieves a significant reduction in size compared to traditional designs, which is crucial for AI robots with limited installation space.
The operational sequence of the actuator involves several stages: signal reception, power conversion, motion transmission, position feedback, and safety protection. When a control signal (e.g., 4-20 mA) is received, the built-in controller processes it and commands the motor to generate torque. This torque drives the nut rotation, which, due to the fixed keyway in the cylinder, converts into linear motion of the screw. The output rod then transfers this motion to the external load, such as an AI robot’s limb or gripper. Throughout this process, the encoder monitors position and feeds data back to the controller, enabling real-time adjustments. In case of anomalies like overload, the electromagnetic brake activates to lock the position and cut power, preventing damage.
This direct drive approach eliminates the need for reducers, reducing backlash and improving response time. Tests show that the actuator can achieve full position adjustment within milliseconds, enhancing the dynamic performance of AI robot systems. The structural integrity is further reinforced through finite element analysis, ensuring that the actuator can withstand repeated cycles and high loads without deformation.
Control System Integration with CANOPEN Bus
For seamless integration into AI robot networks, the actuator employs a CANOPEN bus control system. This protocol allows for robust communication between multiple devices, supporting up to 64 nodes on a single network. The wiring uses shielded twisted-pair cables with 120 Ω termination resistors at both ends to prevent signal reflection. The resistance between CANL and CANH should measure approximately 60 Ω, indicating proper termination.
In practice, the CANOPEN system enables precise coordination of multiple actuators in an AI robot, such as in a robotic arm where synchronized movements are essential. The bus facilitates real-time data exchange, including position, velocity, and fault status, allowing the central controller to make informed decisions. For instance, if an AI robot encounters an obstacle, the actuators can quickly adjust their trajectories based on sensor inputs transmitted via CANOPEN. This level of integration is critical for advanced AI robots operating autonomously in dynamic environments.
To ensure reliability, the communication lines are isolated from high-voltage cables, and the twisted-pair configuration minimizes electromagnetic interference. In long-distance applications, the common ground (GND) is connected across devices to maintain reference potential equality. These measures guarantee stable operation, even in electrically noisy settings common to industrial AI robots.
Performance and Environmental Adaptability
The actuator’s performance was evaluated under various conditions to verify its suitability for AI robot applications. Key tests included thrust endurance, temperature cycling, and vibration resistance. Results indicate that the actuator maintains its rated thrust of 3.5 kN over 100,000 cycles, with no significant wear on the roller screw or motor components. The positioning accuracy remains within 0.5 mm, meeting the requirements for precise AI robot tasks like pick-and-place or assembly.
Environmental testing involved exposing the actuator to temperatures from -55°C to 75°C, as well as humidity levels up to 90% non-condensing. The frameless motor’s vacuum potting process and high-temperature insulation ensure stable operation, while the sealed housing protects internal components from dust and moisture. This makes the actuator ideal for AI robots deployed in challenging environments, such as outdoor inspection or food processing facilities.
Noise levels were measured at 75 dB from 1 meter away, below the 80 dB limit, contributing to a quieter workspace for collaborative AI robots. The electromagnetic brake’s response time of 20 ms ensures quick locking, enhancing safety in emergency scenarios. Overall, these attributes make the actuator a reliable choice for AI robots requiring high performance and durability.
Conclusion and Future Applications
This compact electric actuator represents a significant advancement in actuation technology for AI robots. By incorporating a frameless torque motor, planetary roller screw, and spatial multiplexing design, it achieves high thrust, precision, and compactness. The use of domestic components and CANOPEN control further enhances its appeal for scalable AI robot deployments. Key innovations include a hollow shaft configuration that reduces size, a direct drive system that minimizes backlash, and a dual-mode brake that ensures safety.
Looking ahead, this actuator can be adapted for various AI robot applications, such as exoskeletons, autonomous vehicles, and surgical robots. Its lightweight and efficient design supports the development of more agile and intelligent AI robots, capable of performing complex tasks with minimal human intervention. Future work will focus on optimizing the control algorithms for better integration with AI-based decision systems, as well as exploring materials for further weight reduction. Ultimately, this actuator contributes to the evolution of AI robots as versatile, reliable partners in modern industry and beyond.