We know that robots are advanced and highly intelligent electromechanical devices that can perform a number of daily tasks. This device is capable of responding to its surroundings & making actions to attain a specific task. Robots are made with different components but one of the significant components is the actuator. Generally, actuators are used in almost every machine around us like electronic access control systems, mobile vibrators, household appliances, vehicles, robots & industrial devices. The general actuator examples are; electric motors, jackscrews, stepper motors, muscular stimulators within robots, and many more. This article gives brief information on a robot actuator – working with applications.
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An actuator that is used in robots to make the wheels of the robot turn or robot arm joints turn or to open/close the gripper of the robot is known as a robot actuator. There are different types of robotic actuators are available based on the load involved. Generally, the load is associated with different factors like torque, force, accuracy, speed of operation, power consumption & precision. The working principle of a robot actuator is to change the energy into physical motion and most actuators generate linear or rotary motion.
Robotic actuators are classified into two types according to the requirements of motion like linear motion & rotational motion.
There are two types of actuators used in robots for linear motion activity they are; linear actuators and solenoid actuators.
Linear actuators in robotics are used to push or pull the robot like move forward or backward & arm extension. This actuator’s active end is simply connected to the robot’s lever arm to activate the such motion. These actuators are used in a number of applications in the robotics industry.
Solenoid actuators are special-purpose linear actuators that include a solenoid latch that works on electromagnetic activity. These actuators are mainly used for controlling the motion of the robot and also perform different activities such as a start & reverse, latch, push button, etc. Solenoids are normally used in the applications of latches, valves, locks, and pushing buttons which are controlled normally by an external microcontroller.
There are three types of actuators used in robots for rotational motion activity they are; DC motor, servo motor, and stepper motor.
DC motor actuators are generally used for turning robotic motion. These actuators are available in different sizes with torque generation capability. Thus, it can be utilized for changing speed throughout rotating motions. By using these actuators, different activities like robotic drilling & robotic drive train motion are performed.
Servo motor actuators in robotics are mainly used to control & monitor rotating motion. These are very superior DC motors that allow 360 degrees of rotation, but, continuous revolution is not compulsory. This actuator simply allows halts throughout a rotating motion. By using this actuator, the activity like pick and place is performed. To know how a Pick N Place robot works click on the link.
Stepper motor actuators are helpful in contributing to repetitive rotating activities within robots. So these types of actuators are a combination of both DC & servo motor actuators. These stepper motor actuators are utilized in automation robots where repeatability of activity is necessary.
We know that there are different types of actuators used in robots. Here we are going to discuss how to design a linear actuator that is used in robotics for changing rotating motion into a pull/push linear motion. So this motion can be used to slide, drop, tilt or lift materials or machines. These actuators provide clean & safe motion control that is very efficient & maintained free.
The first consideration while designing a robot actuator is Power. To obtain mechanical power out, it is essential to have power in. So, the amount of mechanical power out can be defined by the load or force to be moved.
The duty cycle can be defined as how frequently the actuator will work & the amount of time it will use. The duty cycle is determined by the actuator’s temperature when it is in motion since power is lost throughout the heat.
When all the actuators are not the same, then there is a difference within their duty cycles. One more factor is the load, which is particularly true of DC motors whereas other factors that can determine the duty cycle are loading characteristics, age & ambient temperature.
The actuator efficiency simply helps in understanding how it will work while in operation. So, the actuator’s efficiency is found by separating mechanical power generated by electrical power.
There are many factors that will extend the actuator’s life are; staying in the rated duty cycle, reducing side load, and staying in the recommended voltage, force, and extreme environments.
Robot actuators are mainly designed for ease of use & efficiency. The design of a linear robot actuator is the inclined plane that starts with a threaded lead screw. This screw provides a ramp to generate force that works along with a larger distance to move any load. The main purpose of robot actuator design is to provide pull/push motion. So, the required energy to provide the motion is manual or any energy source like electricity, fluid, or air. These actuators generally move car seats forwards & backward, open automatic doors, computer disk drives opening and closing.
The robot actuator failure mainly occurs due to many reasons. So these actuators can experience different failures like stuck joints or locked, free-swinging joints & total or partial loss of actuation efficiency. So, these failures will affect robot behavior if the controller of the robot has not been designed with sufficient fault tolerance.
Robot actuators are used for different purposes, so there are many aspects to consider while selecting actuators like
Purpose & Intended Functionality
The necessary actuator type for a specified application mainly depends on the purpose of a robot as well as the intended functionality.
Physical Requirements & Constraints
Whenever the type of actuator is decided to use, then developers must look at the physical requirements & constraints. Because the weight & physical size of the actuator plays a key role while arranging the actuator in the robot otherwise a heavy actuator on a tiny robotic arm may cause to fail the arm in its own weight.
Strength & Power
Based on their particular usage, developers must ensure the strength and power of a specified actuator to perform the task.
Communication Protocol
The communication protocol should also be considered while selecting an actuator for the robot. Many actuators simply support communications with PWM (pulse width modulation) whereas some actuators support serial communications.
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Mounting Space & Options
Developers should verify the mounting space obtainable in or on the robot & the mounting options given by the actuator itself. Because some types of actuators are available with separate mounting hardware that allows you to mount the unit within different orientations whereas others are available with integrated mounting points, which are installed into a particular position & orientation.
Robot actuator advantages include the following.
Robot actuator disadvantages include the following.
The applications of robot actuators include the following.
Actuators are very critical components in the hardware system of robots, mainly responsible for converting energy into the mechanical motion of the robot.
Actuators can be classified in different ways:
By motion type:divided into rotary actuators and linear actuators. Rotary actuators are used to enable the joints of the robot to perform rotary motion, while linear actuators are used for push-pull actions, such as the extension of an arm.
Laifual is one of the top manufacturers of harmonic drives and rotary actuators in China. We have achieved complete our own in-house research and production processes.
By power source: divided into hydraulic, pneumatic, or electric actuators. In humanoid robots, electric actuators are commonly used due to their high precision, low noise, and ease of networked feedback.
Laifual’s rotary actuators can be equipped in robots and powered by electric actuators.
By drive mode: divided into traditional stiffness actuators (TSA), series elastic actuators (SEA), and proprioceptive actuators (PA). Traditional stiffness actuators are mainly composed of motors, reducers, encoders, and torque sensors. Series elastic actuators simulate muscle systems, providing compliance and high energy efficiency. Proprioceptive actuators do not rely on additional force or torque sensors and can directly sense the interaction force between the robot and the external environment.
Currently, traditional stiffness actuators are the mainstream solution, while proprioceptive actuators have been a research hotspot in recent years. Laifual’s rotary actuators use the traditional stiffness actuator (TSA) drive mode.
Key Technical Parameters
The technical parameters of humanoid robots reflect their capabilities and maximum operational performance. The main parameters include degrees of freedom, rated load, workspace, and working accuracy. Here are detailed explanations of some main technical parameters:
Other parameters include working speed, control mode, actuation method, mounting method, power source capacity, robot mass, and environmental parameters, which determine the conditions under which the robot can work. These technical parameters collectively define the performance characteristics of humanoid robots, determining their applicability and efficiency in specific application scenarios. When designing and selecting humanoid robots, these parameters need to be considered based on task requirements and working environments to ensure that the robot can meet the expected work requirements.
On October 1, , Tesla released Optimus at AI Day; on December 14, , Tesla released Optimus-Gen2.
The actuator solutions for Tesla Optimus Gen2 come from: BenMo Research, Robot Heart, Tesla official website, Great Wall Securities Industrial Financial Research Institute. Note: The units of numbers are in pieces.
Linear Actuator
The configuration of the Tesla Optimus linear actuator is: frameless torque motor1 + planetary roller screw1 + force sensor1 + encoder1 + driver + ball bearing1 + four-point contact ball bearing1.
Tesla Optimus linear actuator structure, source: Tesla
Rotary Actuator
The configuration of the Tesla Optimus rotary actuator is: frameless torque motor1 + harmonic reducer1 + torque sensor1 + encoder2 + driver1 + cross roller bearing1 + angular contact ball bearing*1.
Tesla Optimus rotary actuator structure, source: Tesla
Laifual Achieves Independent Research and Production of Core Robot Components
Core components of actuators include motors, reducers, screws, encoders, and torque sensors.
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Motor: The "blood vessel" of the actuator system. It drives mechanical components to achieve specific movements based on torque, speed, and position command signals received. Additionally, various sensors in the motor, such as encoders and force sensors, provide real-time operational information of the motor and mechanical components back to the driver and controller, enabling precise motion control. The actuator's drive source can be a DC motor, AC motor, stepper motor, or servo motor, depending on the required torque, speed, accuracy, and control requirements. Humanoid robots mainly use frameless torque motors with high integration, precision motion control, and efficient torque output. Harmonic Reducer: The bridge between the motor and the transmission device. Its function is to convert the high-speed, low-torque power output by the servo motor into low-speed, high-torque power, enabling the robot to bear greater loads and drive the robot joints. Due to motor manufacturing technology limitations, reducers and motors are usually used together in robot actuators. Common types of reducers include harmonic reducers, planetary reducers, and RV reducers. Laifual, as a globally renowned manufacturer, has been focusing on producing harmonic reducers for over 10 years. As a top 3 manufacturer in the Chinese market, Laifual has a market share of up to 9%, providing strong technical and experience support for module development. Encoder: The feedback device for drive and control information. It is used to measure and provide feedback on the position, speed, and acceleration of the actuator. Installed on the servo motor, it converts angular displacement (code disc) or linear displacement (code scale) into electrical signals to provide feedback on the rotor position and speed, converting the obtained motion information into pulse signals and sending them to the driver for information comparison, ensuring closed-loop control. Encoders can be optical, magnetic, or mechanical, providing the necessary feedback information for closed-loop control. Commonly used encoders in robots include optical encoders and magnetic encoders. Currently, optical encoder technology is more mature and offers higher precision. Magnetic encoders theoretically have lower costs and promising future prospects.