Inertial Sensors for Humanoid Robots
Inertial sensors play a key role in humanoid robots. They can sense the robot’s motion state and posture changes in real time, and provide important data support for the robot’s stable walking, balance control and precise movements.
Introduction
With the rapid development of science and technology, humanoid robots, as an important part of future intelligent life, are gradually moving from science fiction movies to reality. Humanoid robots can not only perform various complex tasks, but also interact naturally with humans. Their research and development and application fields involve multiple industries such as industry, medical care, and services.
Inertial sensor applications
Among the many core components of humanoid robots, inertial sensors play a vital role. This article will introduce in detail the application of inertial sensors in humanoid robots, including their principles, functions, advantages, technical challenges, and market status.
Overview of inertial sensors
1. Definition and principle
Inertial sensors, full name inertial measurement units (IMUs), are devices that can measure the angular velocity and acceleration of objects in three-dimensional space. IMUs are usually composed of gyroscopes and accelerometers, and some high-end IMUs may also include other sensors such as magnetometers.
Gyroscopes are used to measure the angular velocity of an object, that is, the rotation speed of an object around each axis; accelerometers are used to measure the linear acceleration of an object in three axes. By fusing the data of gyroscopes and accelerometers, IMUs can sense the posture (such as pitch, yaw and roll) and motion state of an object in real time.
Inertial sensors—applications and challenges in a nutshell
2. Classification and accuracy
Depending on the accuracy and application scenarios, IMUs can be divided into consumer, industrial and tactical (or military) grades. Consumer-grade IMUs have low accuracy and relatively low cost, and are mainly used in consumer electronics such as smartphones and wearable devices; industrial-grade IMUs have high accuracy and are suitable for drones, self-driving cars and other fields; tactical-grade IMUs have extremely high accuracy and stability, and are widely used in military and aerospace fields such as missile guidance and satellite attitude control.
In the field of humanoid robots, industrial-grade or near-tactical-grade IMUs are usually used due to the need to achieve high-precision attitude control and motion tracking. For example, Tesla’s Optimus humanoid robot has a built-in high-performance IMU to achieve complex dance movements and stable walking posture.
Application of inertial sensors in humanoid robots
1. Balance control
Balance control is one of the most basic and important functions of humanoid robots. Since humanoid robots have the characteristics of walking on two legs, their balance stability is directly related to the safety and reliability of the robot. IMU provides accurate feedback signals to the control system by sensing the inclination, rotation and other posture changes of the robot’s body in real time. When the robot encounters an uneven road surface or is disturbed by external forces, the IMU can quickly detect the inclination angle and speed changes of the body. The control system adjusts the robot’s pace and center of gravity position based on this information to maintain balance and prevent falls.
For example, during the walking process of a bipedal robot, the IMU can monitor the robot’s leg swing angle, body inclination angle, angular velocity and other parameters in real time. When one foot of the robot leaves the ground, the other foot needs to bear all the weight. At this time, the IMU data is crucial for adjusting the center of gravity position of the robot. By precisely controlling the torque and angle of the leg joints, the robot can maintain a stable posture during the single-leg support phase and prepare for the next step of walking.
2. Motion tracking and posture adjustment
In addition to balance control, IMU can also be used for motion tracking and posture adjustment of humanoid robots. When the robot performs complex movements, such as reaching out to grab, climbing stairs, jumping, etc., the IMU can measure the robot’s angular velocity and acceleration changes in real time, providing accurate motion information for the control system. By fusing the IMU data with the information of other sensors (such as visual sensors, force sensors, etc.), the control system can accurately control the robot’s joint movement and posture changes, so that the robot can accurately and stably perform the predetermined actions.
For example, when the robot reaches out to grab an object, the IMU can monitor the angular velocity and acceleration changes of the robot’s arm in real time, as well as the relative position relationship between the arm and the object. The control system adjusts the arm’s joint torque and angle based on this information, so that the robot can accurately grab the object and maintain a stable posture.
3. Navigation and positioning
Although IMU itself cannot be directly positioned, it can be used in conjunction with other sensors such as GPS, visual sensors, and lidar to achieve robot positioning and navigation. In environments where GPS signals are weak or cannot be covered (such as complex environments such as indoors or urban canyons), IMU can provide the robot’s movement speed and direction information, and combine the data of other sensors to perform dead reckoning to help the robot determine its own position and movement trajectory.
For example, in humanoid robots with autonomous navigation, IMU can be combined with sensors such as visual sensors and lidar to achieve accurate map construction and positioning. Visual sensors are used to identify feature points or landmarks in the environment, while lidar is used to measure the distance and angle information between the robot and the surrounding environment. IMU provides the robot’s movement speed and direction information. By fusing these data, the robot can build an accurate environmental map and achieve autonomous navigation and obstacle avoidance functions.
4. Environmental perception and obstacle avoidance
IMU can also be used for environmental perception and obstacle avoidance functions of humanoid robots. By sensing the relative motion relationship between the robot and the surrounding environment (such as speed, acceleration, and angular velocity), IMU can provide the robot with environmental perception capabilities.
When the robot encounters an obstacle, IMU can detect the relative speed and direction changes between the robot and the obstacle, helping the robot to determine the position and movement trend of the obstacle, and thus make corresponding obstacle avoidance strategies.
For example, when the robot encounters a sudden obstacle during walking, IMU can monitor the inclination angle and speed changes of the robot body in real time.
If the robot is detected to have a risk of colliding with an obstacle, the control system can adjust the robot’s pace and posture according to the IMU data to avoid collision with the obstacle. At the same time, IMU can also be combined with other sensors (such as visual sensors, sonar sensors, etc.) to achieve more accurate environmental perception and obstacle avoidance functions.
robot sensors definition
Advantages of inertial sensors in humanoid robots
1. Not subject to environmental interference
Compared with other sensors (such as visual sensors, lidar, etc.), IMU has the advantage of not being subject to environmental interference. Visual sensors are easily affected by factors such as lighting conditions and obstructions, resulting in reduced perception accuracy; LiDAR is easily affected by weather conditions such as rain, fog, and dust, resulting in increased errors in measuring distance and angle. IMU is not affected by these factors and can work stably in various complex environments.
2. High real-time performance
IMU has extremely high real-time performance and can perceive the posture and motion state of objects in real time. This is crucial for humanoid robots that need to respond quickly. For example, when a robot encounters an emergency during walking, IMU can quickly detect the tilt angle and speed changes of the body. The control system adjusts the robot’s gait and posture in time based on this information to maintain balance and stability.
3. Strong independent working ability
IMU has the ability to work independently and can continue to work even in the absence of external signals. This is especially important for humanoid robots that need autonomous navigation and obstacle avoidance. For example, in an environment where the GPS signal is weak or cannot be covered, IMU can provide the robot’s movement speed and direction information, and combine the data of other sensors for dead reckoning to achieve autonomous navigation functions.
4. Good concealment
IMU has good concealment and is not easily interfered with or detected. This is of great significance for application scenarios that require high confidentiality (such as military reconnaissance, counter-terrorism operations, etc.). For example, in a military reconnaissance robot, the IMU can provide the robot’s posture and movement information without exposing the robot’s location and whereabouts.
2025 ieee ras international conference on humanoid robots
Technical Challenges of Inertial Sensors in Humanoid Robots
1. Error Accumulation Problem
The error of IMU will accumulate over time. Since IMU calculates the posture and motion state of an object by integrating the data of accelerometers and gyroscopes, any small measurement error will gradually accumulate and increase over time. This will cause deviations in the calculation results of the robot’s posture and motion state, affecting the performance and reliability of the robot.
In order to solve the error accumulation problem, methods such as Zero Velocity Update (ZUPT) algorithm or magnetometer-assisted correction are usually used. The zero velocity update algorithm corrects and updates the IMU data when the robot is stationary or the speed is zero; the magnetometer-assisted correction uses the magnetometer to measure the direction and intensity of the earth’s magnetic field to assist in correcting the IMU’s posture data.
2. Cost Issue
High-performance IMUs usually have a high cost. Since IMUs need to integrate high-precision sensors such as gyroscopes and accelerometers, and require complex signal processing and data fusion algorithms, their cost is relatively high. This is an important challenge for humanoid robots that need to be mass-produced and applied.
In order to reduce costs, MEMS (micro-electromechanical system) technology can be used to manufacture IMU. MEMS IMU has the advantages of small size, low power consumption, low cost, etc., and can meet the needs of most application scenarios. However, the accuracy and stability of MEMS IMU are relatively low, and its performance needs to be improved through advanced signal processing and data fusion algorithms.
3. Fusion algorithm problem
In order to achieve high-precision posture control and motion tracking, the data of IMU needs to be fused with the data of other sensors. However, due to the different measurement principles and data characteristics of different sensors, how to perform effective data fusion is a challenging problem.
In order to solve the fusion algorithm problem, algorithms such as Kalman Filter, Extended Kalman Filter or Particle Filter are usually used. These algorithms can be adaptively adjusted and optimized according to the different sensor data characteristics and the needs of application scenarios to achieve high-precision data fusion and posture estimation.
humanoid robots
Market status and development trend of inertial sensors in humanoid robots
1. Market status
At present, the global IMU market is mainly dominated by several international manufacturers, including Bosch in Germany, STMicroelectronics in France, Murata in Japan, and Honeywell in the United States. These manufacturers have rich experience and advantages in IMU technology, production and application, and occupy most of the market share.
In the field of humanoid robots, due to the need to achieve high-precision posture control and motion tracking functions, the performance and accuracy of IMUs are required to be high. However, there are relatively few IMU products on the market that can meet the needs of humanoid robots, and most of them rely on imports. This limits the development and application promotion of humanoid robots.
In order to break this situation, some domestic companies have begun to increase their R&D investment and production efforts in IMU technology. For example, companies such as Huace Navigation, StarNet Yuda, and Minxin Shares have begun to get involved in the IMU field and have launched a series of high-performance IMU products for humanoid robot applications. The launch of these products not only improves the competitiveness of the domestic IMU market, but also provides strong support for the development of humanoid robots.
2. Development Trend
With the continuous development of technologies such as artificial intelligence, the Internet of Things and big data, humanoid robots will be more widely used and promoted in the future. This will drive the rapid growth and development of the IMU market. It is expected that in the next few years, the IMU market will show the following development trends:
- Accelerated domestic substitution (continued):
With the continuous enhancement of domestic scientific and technological strength and the continuous improvement of the industrial chain, domestic substitution will become an important trend in the IMU market. Domestic companies will increase their investment in IMU research and development, production and application, and launch more high-performance IMU products with independent intellectual property rights to meet the needs of high-end application fields such as humanoid robots. This will not only reduce the manufacturing cost of humanoid robots, but also improve the international competitiveness of the domestic IMU industry. - Multi-sensor fusion technology:
In the future, IMU will be more closely integrated with other sensors (such as visual sensors, lidar, force sensors, etc.) to form a multi-sensor fusion system. By fusing data from different sensors, more accurate and comprehensive environmental perception and posture control can be achieved, and the intelligence level and adaptability of humanoid robots can be improved. For example, combining the data of visual sensors and IMUs can achieve more accurate navigation and obstacle avoidance functions; combining the data of force sensors and IMUs can achieve more sophisticated operations and force control. - Miniaturization and low power consumption:
With the continuous development of micro-electromechanical systems (MEMS) technology, IMUs will gradually develop in the direction of miniaturization and low power consumption. Miniaturization will make IMUs easier to integrate into devices such as humanoid robots, reducing the size and weight of the equipment; low power consumption will extend the battery life of the equipment and improve the practicality of the equipment. This will provide more possibilities for the design and manufacture of humanoid robots and promote the popularization and application of humanoid robots. - Intelligent algorithms:
In the future, with the continuous development of artificial intelligence technology, IMU data processing and analysis will be more intelligent. By introducing algorithms such as deep learning and machine learning, more accurate and efficient posture estimation and motion tracking can be achieved. This will improve the intelligence level of humanoid robots and enable them to better adapt to complex and changing environments and task requirements.
Specific application cases of inertial sensors in humanoid robots
1. Boston Dynamics Atlas Robot:
Boston Dynamics’ Atlas robot is one of the well-known humanoid robots in the industry. It has a built-in high-precision IMU for balance control, motion tracking, and posture adjustment. In the demonstration video, we can see that the Atlas robot can stably walk, jump, climb, and carry objects in various complex environments, which is inseparable from the precise perception and control of the IMU.
Humanoid robots in China
2. Tesla Optimus Robot:
Tesla’s Optimus robot is one of the most watched humanoid robots in recent years. It also has a built-in high-performance IMU for precise dance moves and stable walking postures. At Tesla’s press conference, the Optimus robot demonstrated its flexible posture and coordinated movements, which fully demonstrated the application potential of IMU in humanoid robots.
3. Service Robot:
In the field of service robots, IMUs also play an important role. For example, restaurant service robots need to be able to walk stably in crowded environments to avoid collisions with customers or obstacles. With the built-in IMU, the service robot can sense its own posture and motion state in real time, make corresponding adjustments, and ensure the stability and safety of walking.
4. Medical rehabilitation robot:
Medical rehabilitation robot is an important device to help patients with rehabilitation training. With the built-in IMU, the medical rehabilitation robot can monitor the patient’s motion state and posture changes in real time, and provide accurate feedback and guidance for rehabilitation training. This helps to improve the effect of rehabilitation training and the patient’s recovery speed.
Future prospects of inertial sensors in humanoid robots
1. Higher precision, lower cost:
With the continuous advancement of technology, the accuracy of IMU will continue to improve, and the cost will gradually decrease. This will enable more humanoid robots to use high-performance IMUs, improving their intelligence level and adaptability.
2. Wider application areas:
With the continuous development and popularization of humanoid robots, the application areas of IMU will also be more extensive. In addition to the traditional industrial, medical and service fields, humanoid robots will gradually enter the fields of home, education, entertainment, etc., bringing more convenience and fun to people’s lives.
3. More in-depth integration and innovation:
In the future, IMU will be more deeply integrated and innovated with other sensors and technologies. For example, combined with IoT technology, remote monitoring and control of humanoid robots can be realized; combined with virtual reality technology, humanoid robots can be provided with richer interactive experience and environmental perception capabilities.
humanoid robot servo
In summary, inertial sensors play a vital role in humanoid robots. With the continuous advancement of technology and the continuous expansion of application fields, IMU will play a more important role in the field of humanoid robots and promote the development and popularization of humanoid robots.
At the same time, we also look forward to more innovations and technological breakthroughs to bring more possibilities and opportunities for the application of inertial sensors in humanoid robots.
Inertial Sensors for Humanoid Robots PDF Download
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FAQs
The following are frequently asked questions and answers about the use of inertial sensors in humanoid robots:
Inertial sensors are an important component of humanoid robot proprioception sensors. They can sense the robot’s posture, acceleration and other information in real time, assist the robot in correcting the predetermined walking mode, prevent falls, and achieve dynamic and stable walking motion.
Inertial sensors provide accurate data support for the control system by measuring the robot’s angular velocity and acceleration in three orthogonal directions, enabling the robot to adjust its walking posture according to actual conditions to maintain balance.
The commonly used inertial sensors in humanoid robots mainly include MEMS inertial sensors (such as MEMS accelerometers and MEMS gyroscopes) and fiber optic inertial sensors. Among them, MEMS inertial sensors are widely used in humanoid robots due to their small size, light weight, and low power consumption.
The challenges faced by inertial sensors in humanoid robots mainly include the complexity of error sources (such as random noise, errors caused by temperature changes, etc.), the low localization rate of high-precision sensors, and how to accurately perceive the robot’s motion state in a complex environment.
Improving the performance of inertial sensors in humanoid robots can be achieved by optimizing sensor design, improving manufacturing process level, using advanced error compensation algorithms, and fusing data with other sensors (such as visual sensors, force sensors, etc.).
The commonly used inertial sensors in humanoid robots are inertial measurement units (IMUs), which combine gyroscopes and accelerometers to simultaneously measure the angular velocity and acceleration of an object in three orthogonal directions.
Compared with technical routes such as motion capture using optical/machine vision, passive exoskeletons, and manual guidance, IMUs can effectively avoid obstacle occlusion problems and the execution of complex movements, and are not interfered by the external environment. They are the most feasible solutions for assisting humanoid robots in achieving bipedal movement.
The accuracy of IMUs directly affects the balance, stability, and accuracy of motion trajectories of humanoid robots. High-precision IMUs can provide more accurate data support, enabling robots to better adapt to complex environments and complete more sophisticated tasks.
There are many companies in China that are developing inertial sensors for humanoid robots, such as Zhonghaida and Minxin Co., Ltd. With their technical accumulation and product advantages in the field of inertial sensors, these companies are expected to provide high-quality inertial sensor products for humanoid robots.
With the continuous development of humanoid robot technology and the expansion of application scenarios, the requirements for the accuracy, stability and reliability of inertial sensors will become higher and higher. In the future, inertial sensors will develop in the direction of higher accuracy, smaller size and lower power consumption to meet the needs of humanoid robots for high-performance sensors.
Inertial sensors in humanoid robots usually refer to inertial measurement units (IMUs), which are electronic devices that integrate accelerometers and gyroscopes to accurately measure and monitor key information such as acceleration, angular velocity, and direction of objects.
The working principle of inertial sensors is based on the inertial characteristics of objects. Accelerometers measure the acceleration of objects in linear motion, while gyroscopes detect the angular velocity of objects in rotational motion, together providing the robot with comprehensive information about its motion state.
Accelerometers can measure the linear acceleration of robots along three orthogonal axes, helping robots sense changes in their motion state, such as starting, stopping, accelerating, or decelerating. This is essential for robots to maintain balance, adjust gait, and perform precise positioning.
Gyroscopes use the principle of conservation of angular momentum to detect the rotational motion of objects. It has a high-speed rotating object (such as a micromechanical oscillator) inside. When the external rotational force is applied to the gyroscope, the axis of the rotating object will try to maintain its original direction, thereby generating a measurable electrical signal reflecting the magnitude and direction of the external angular velocity.
By continuously monitoring the acceleration and angular velocity of the robot, the IMU can calculate the robot’s posture (such as pitch, yaw and roll angle) in real time. When the robot detects that the posture deviates from the predetermined value, the control system will adjust according to the information provided by the IMU to maintain balance and stability.
MEMS IMU (microelectromechanical system inertial measurement unit) is a commonly used type of IMU in humanoid robots. It uses microelectromechanical system technology to integrate sensors such as accelerometers and gyroscopes on a tiny chip. It has the advantages of small size, light weight, low power consumption and low cost, and is very suitable for humanoid robots with strict requirements on size and weight.
The accuracy of IMU directly affects the perception of motion state of humanoid robots. High-precision IMU can provide more accurate data, enabling robots to better adapt to complex environments and improve the accuracy and stability of motion control. On the contrary, low-precision IMU may cause the robot to move unsteadily or even fall.
IMU is widely used in humanoid robots, including but not limited to: posture control, balance maintenance, gait adjustment, navigation positioning, motion trajectory tracking, etc. By integrating with other sensors (such as visual sensors, force/torque sensors, etc.), IMU can further enhance the robot’s intelligence level and autonomous navigation capabilities.
