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Servos as robot components

Robotic Arm with Servo Motors — A Step Closer to Future

In 1942, when Isaac Asimov first voiced three Laws of Robotics, the smart machines co-existing in symbiosis with people seemed more of a fiction than a probable reality. Today, state-of-the-art technology opens up a breathtaking perspective of robots penetrating into our lives.

At home, the intelligent devices do the drudgery we hate—the cleaning and washing. At work, repetitive, dirty, and dangerous tasks are as easy as one-two-three for a robotic arm with servo motors. The type of engine provides accuracy, smoothness, and flexibility of motion comparable to a human limb, while excelling it at repeatability.

robotic arm
PULSE by Rozum Robotics

General data: definition and applications

A robotic arm is a programmable mechanism comprising two or more segments linked by means of joints into a kinematic chain. Each joint in the chain is a servo or another motor providing either rotational or linear displacement of the segments. The number of linkages in the structure defines how many freedom degrees (DOF) it has—typically, ranging from two to the human arm maximum of seven.

Six DOF robotic arm with servo motors

A manipulator is smaller than an industrial robot, enabling flexibility of usage and relocation, as well as optimized floor space utilization. More advanced collaborative models can even work alongside people with no safety cages.

Within the general category, it is also possible to  distinguish the following subtypes, corresponding to different types of provided movement:

  1. Cartesian
  2. Cylindrical
  3. Spherical
  4. Articulated
  5. SCARA
  6. Parallel
  7. Anthropomorphic 

The terminal component in the machine is an end effector intended to handle versatile jobs, depending on the type of application.

Mostly, these are unvaried and rather dull works, in particular:

  1. welding
  2. painting
  3. material handling
  4. assembling
  5. palletizing

Though requiring little intellectual efforts, the operations demand extra carefulness, unfailing attention, and tirelessness—a challenge when we speak about a human. At least, to maintain over extended periods without rest. Manipulators possess all the necessary qualities to meet the demands, posing viable alternative to human labour. 

A robotic arm and servo motors

To become functional, an arm requires a device to furnish it with force in sufficient quantities to lift joints—an actuator. Though latest progressive findings have resulted in invention of novelty drives, such as biomotors, a typical robotics-oriented actuation mechanism is a stepper or a servo.

Technical details:

Biomotors are actuation solutions relying on contraction-release effects emerging in a special type of material—biometal—under voltage. Its reaction to a low-voltage impulse is slower than response of a conventional electrical motor, but its motion output possesses a quality of extra value—smoothness.


biometal operation principle

Both engines are known to ensure precise positioning over multiple work cycles, which is of critical importance for a manipulator to cope with its usual tasks. Steppers have low price and give little configuration or maintenance problems, whereas servos are more troublesome to set up and pricy. Nevertheless, servomechanisms boast properties of value in a robotic application: comprehensive motion feedback, outstanding governability, uniform and stable torque production over the entire performance curve.

In PULSE robotic solutions, servomechanisms are behind the following features and benefits:

  • High torque density. In-built metal-gear gearheads make it possible to multiply torque output of the brushless AC motor by the factor of nearly one hundred without impacting the overall servo dimensions. The underlying strain-wave technology entails the additional advantage of near-zero backlash, minimizing efficiency losses. 
  • Movement flexibility. PULSE robotic arms have six degrees of freedom—almost as many as a person’s arm. Embedded into joints, servo motors enable their precise angular displacement within the span from -360 to +360 degrees. Additionally, the engines ensure positioning of the work tool with a thousandth degree accuracy. A standard ISO 9409-1-50-4-M6 mechanical interface at the end effector connection facilitates integration. Since the arm has a modular construction, customers are welcome to experiment with designs and configurations to enhance flexibility properties.
  • High-precision movement control. Servo actuators rely on feedback from two encoders taking measurements before and after gearing. The sensing devices watch out for change of positions, transferring the collected data to a controller, also seated inside the servo housing. The controller module acts as a intellectual hub, processing the feedback to establish what needs to be adjusted to achieve desired propulsion.
  • Programmability. The governing routine is the responsibility of the controllers. The devices are printed board microprocessors that communicate with external masters to receive commands and report on their execution. Supported communication methods include the CANOpen protocol and an Application Programming Interface (API) in C, Java, and Python. Both methods are easy to set up within minutes, literally taking a few command code strings to launch communication.


  • Reliability and durability. Most of the components in RDrive servomechanisms are self-designed and self-produced. This translates into continuous quality control throughout stages of a product life cycle and traceability of manufacturing defects, should they occur. The guaranteed life-in-service is 35,000 hours—both for actuators and the PULSE solution as a whole. Modular construction makes it possible to replace servos with minimum efforts.
  • Safety. Each actuator is fitted out with overtemperature protection based on sensors integrated into their brushless cores. CANOpen and API communication interfaces offer specialized safety features to detect abnormal operation and to stop or set up servos to react to the abnormalities.

As separate products, RDrive models can be customized to drive any other robotic solution: by varying the form factor, modifying the mountings, changing the communication type, etc.

Fancy the future

Powering a robotic arm, servo motors aid the humanity in building a better future. In the fancy world of tomorrow, people are supposed to embrace creativity, whereas robots are to act as their fatigueless and ever-attentive collaborators. In other words, people are expected to give birth to ideas, and machines—to nurture them to the adulthood of becoming a tangible asset. 

Examples are already abundant when smart machines replace people in dangerous and boring occupations, such as attending assembly lines or working with chemicals. Multiple research report considerable savings achieved through automating industrial workflows with robots.


mind-guided prosthetics

Evolution of servomechanisms gives rise to new capabilities in robotics. Ultra-precise micromotors in robotic hands used as end effectors can already mimic minute flexes of fingers. Introduction of novelty control methods, including the brain-machine interface, hold out the promise of major breakthroughs in heavy-duty manufacturing and prosthetic medicine.

Imagine a workshop with no people around, all of them sitting in remote cabins, relaxed in comfortable chairs, and making smart mechanisms lift cargoes with just the power of their thought.

Or fancy the disabled getting a chance to enjoy unrestricted movement again!