Comprehensive Analysis of Servo Systems and Sensor Configurations of Three Representative Collaborative Robots

Meta Description: In-depth analysis of servo drives and sensor technologies in YASKAWA MOTOMAN-HC10, Universal Robots UR5, and SIASUN 7-axis collaborative robots. Explore torque sensors, safety perception systems, and dual closed-loop control mechanisms that enable safe human-robot collaboration, low-cost deployment, and high flexibility. Discover the core technological pathways of collaborative robots in the Industry 4.0 era.

Keywords: Collaborative Robots, Torque Sensors, Joint Torque Sensors, Safety Sensors, Servo Drives, Dual Closed-Loop Control, Kinematic Redundancy, 7-DOF Robots, Human-Robot Collaboration, Safety Perception, Industry 4.0 Collaborative Robots, YASKAWA HC10, Universal Robots UR5, SIASUN 7-Axis, Nexisense

As a key driving force in the transformation of the manufacturing industry, collaborative robots have gained widespread attention only in recent years. However, the concept itself dates back to the 1990s. Designed around the principle of “coexistence with humans,” this new generation of robots abandons the traditional reliance on safety fences, allowing humans and robotic arms to work efficiently within the same space. The advantages are clear: high safety, low deployment costs, strong adaptability across diverse scenarios, and intuitive, easy-to-learn operation. These characteristics significantly lower the barrier for small and medium-sized enterprises to adopt automation, while also accelerating the deep implementation of Industry 4.0.

According to industry forecasts, from 2015 to 2020, the collaborative robot market expanded more than tenfold, with market value surging from USD 95 million in 2014 to USD 1 billion. Lightweight models have become particularly popular, with expected prices dropping to the range of USD 15,000–20,000. TechNavio further reported that by 2019, the global collaborative robot market achieved a compound annual growth rate of 50.88%. Behind these impressive figures lies continuous technological innovation—especially the optimization of servo systems and sensor configurations. In this article, we take three globally representative models as entry points, dissecting their underlying technologies to reveal how precise sensing and control enable truly harmonious human-robot coexistence.

Technical Highlights of the Three Representative Models

In the collaborative robot sector, Japanese, European, and Chinese brands each follow distinct technological paths while converging on safety and flexibility. Below, we analyze classic models from YASKAWA, Universal Robots, and SIASUN, examining how their servo and sensor configurations support core functionalities.

YASKAWA MOTOMAN-HC10: A Japanese Benchmark with Safety as the Priority

The MOTOMAN-HC10 launched by YASKAWA Electric focuses on “plug-and-play” functionality and “zero-barrier safety,” addressing two major pain points in traditional robot deployment: high-cost safety light curtains and complex operation. All joints of the HC10 integrate high-precision torque sensors capable of real-time monitoring of external torque variations, with typical resolution reaching 0.1 N·m. Once human contact is detected, the system immediately activates power and force limiting mechanisms, enabling instant stop or compliant retreat to prevent potential injury.

Additionally, the HC10’s arms are covered with blue flexible shock-absorbing material. This high-elasticity exterior effectively absorbs collision impacts, reducing peak contact forces to a minimum. Even in accidental collisions, risks are maintained within acceptable limits. Notably, its compact, integrated servo drives are built directly into the joints, shortening cable lengths and significantly reducing electromagnetic interference (EMI/RFI), thereby enhancing overall system stability. This combination of “hardware sensing redundancy + physical buffering” made the HC10 one of the first commercially available collaborative robots that operate without additional safety fences—ideal for rapid deployment in small and medium-sized enterprises.

In practical applications, the HC10 is widely used in assembly lines and material handling scenarios, seamlessly collaborating with operators. The following image illustrates the HC10 safely coexisting with humans in a factory environment, clearly highlighting the blue exterior and joint sensor locations:

Universal Robots UR5: A Pioneering European Standard

As the world’s first commercially available collaborative robot, the UR5 debuted in 2009 and established the genetic blueprint for modern collaborative robots: modular design, graphical programming, and robust sensing capabilities. The UR5 integrates a six-axis force/torque sensor in its wrist, capturing three-axis forces and three-axis torques simultaneously. This enables precise force-controlled operations such as compliant assembly, surface polishing, and drag teaching. Consequently, it excels in electronics manufacturing and similar fields, achieving end-effector repeatability of ±0.03 mm.

The UR5 employs ultra-compact servo drives mounted close to each joint, paired with absolute encoders exceeding 19-bit resolution to form a dual closed-loop control system consisting of speed and position loops. This configuration ensures high dynamic response and stability. Its multi-layered safety perception system includes joint torque monitoring, speed limitation, separation monitoring zones, and emergency stop logic—totaling 15 safety functions that fully comply with ISO/TS 15066 standards. The UR5’s standout advantage lies in usability: through drag teaching and a touchscreen interface, even non-specialized workers can become proficient within hours, dramatically lowering traditional robot programming barriers.

SIASUN 7-Axis Flexible Collaborative Robot: A Breakthrough in Domestic Flexibility

SIASUN’s 7-axis flexible multi-joint collaborative robot is often described as having “Tai Chi-like flexibility” and represents China’s first commercially available 7-degree-of-freedom collaborative robot. Designed for confined spaces, complex postures, and repetitive twisting operations, it supports rapid configuration, hand-guided teaching, vision guidance, and collision detection. The 7-DOF kinematic redundancy is its core advantage: compared to traditional 6-axis robots, the additional degree of freedom enables more approach postures, easier avoidance of singularities and obstacles, and superior performance in automotive interiors, aerospace, and medical device assembly.

All joints are equipped with high-precision torque sensors, enabling real-time collision detection and constant-force operations. The dual closed-loop high-performance servo system uses incremental encoders and Hall sensors at the reducer front end for speed feedback, while a 19-bit high-resolution absolute encoder at the output provides position feedback—significantly improving dynamic accuracy. A comprehensive safety perception matrix, including torque monitoring, speed limitation, and zone protection, further strengthens human-robot collaboration safety. In complex movements within narrow cavities, this robot demonstrates unparalleled flexibility.

Core Characteristics of Collaborative Robots and Their Technical Foundations

Unlike traditional industrial robots, collaborative robots emphasize seamless integration with humans. This requires a balanced approach across four dimensions: flexibility, usability, safety, and cost control—each underpinned by servo systems and sensors.

Flexibility is the soul of collaborative robots. Through kinematic redundancy designs such as SIASUN’s 7-axis configuration, robots achieve multi-angle operation in confined spaces, overcoming the limitations of traditional 6-axis structures. Usability is reflected in drag teaching and graphical interfaces that reduce dependence on specialized programming. Safety relies on multi-layer perception systems that prevent collisions in fence-free environments. Cost efficiency is achieved through integrated servos and modular architectures that reduce additional hardware investment.

These features are enabled by advanced technological integration. Miniaturized servo drives installed within joints create compact structures and enhance interference resistance. Dual closed-loop control algorithms optimize positioning accuracy, ensuring stability during high-speed motion. Torque sensors serve as the “sense of touch,” detecting subtle force changes and enabling immediate response. Safety sensors such as laser scanners or cameras provide environmental awareness to prevent accidents. Part detection sensors ensure reliable gripping when vision systems are absent.

Across all three representative models, a clear consensus emerges: integrated servo drives ensure compactness; dual closed-loop control enhances precision; high-accuracy torque sensors are critical for collision detection; and multi-layer safety perception forms redundant protection. As an industrial sensor specialist, Nexisense offers joint torque sensors, six-axis force sensors, and safety proximity sensors featuring high accuracy, low latency, and strong anti-interference performance. These solutions have been widely adopted by collaborative robot manufacturers to optimize force control and safety detection.

Frequently Asked Questions

• What is the main difference between collaborative robots and traditional industrial robots? Traditional robots require isolated operation, while collaborative robots emphasize human coexistence, enabling safe interaction through sensors, offering greater flexibility and lower deployment costs.

• What role do torque sensors play in collaborative robots? They monitor joint torque changes in real time to detect collisions or abnormal forces, enabling immediate stop or force adjustment to ensure safety.

• Why are 7-axis robots better suited for complex environments? Additional degrees of freedom provide redundant postures, allowing obstacle avoidance, singularity prevention, and improved flexibility and fault tolerance.

• How should small and medium-sized enterprises choose collaborative robots? Prioritize ease of use and cost efficiency, such as the UR5’s graphical programming or the HC10’s fence-free design, and match sensor configurations to specific application scenarios.

• What are the future trends in collaborative robot technology? Sensing precision will continue to improve, with deeper integration of AI vision and smarter servo systems, driving expansion into more refined application scenarios.

Conclusion

From the safety-ready deployment of the YASKAWA HC10, to the usability pioneered by the UR5, and the flexibility breakthrough of the SIASUN 7-axis robot, these three representative models illustrate the essence of collaborative robotics: achieving harmonious human-machine integration through precise coordination between servo systems and sensors. As manufacturing continues its transition toward intelligent automation, demand for these technologies will only intensify. Domestic brands such as Nexisense are accelerating the journey from emerging technology to factory standard by delivering reliable sensor solutions. Embracing this transformation not only enhances productivity but also reshapes the boundaries of human-robot interaction.