How Motor Drive Innovation Can Help Solve Robot Motion Design Challenges

From assisting in surgery to lifting thousands of kilograms in manufacturing plants, robots facilitate many aspects of our lives. The impact of robots on the modern world is obvious, but have you ever thought about how robotic systems achieve such precise, fast and powerful movement? If the answer is via the motor, congratulations!

Robots tend to imitate operations that would be performed by humans; as such, their functionality primarily consists of adjusting position and orientation through some form of displacement or rotation, typically through motors.

While traditional robotics applications focused primarily on mechanical actuation (such as arm manipulation or conveyor belt looping), modern applications are much simpler, like camera rotation or precision mechanical beam steering for lidar sensors. You might be surprised to know that the most basic applications of electric motors are fans and pumps, but they actually play important roles in cooling and hydraulics.

Click on image to jump to video: Learn how TI is using innovative semiconductors to enhance robot performance

For example, a brushless DC (BLDC) motor in a robotic arm joint (shown in Figure 1) typically consists of a rotating rotor and a stationary stator. Applying an electrical signal to energize the coil windings on the stator creates a magnetic field, which generates magnetic force that moves the rotor, which in turn rotates the joints within the robotic arm. By rationally using electronic signals, the robotic arm will not only move, but also move at a specific speed, position accuracy and torque.

Figure 1: Cross-sectional view of BLDC motor structure

How electric motors will power the next generation of robots

In addition to precise and powerful tasks involving motion, advances in motor control semiconductors such as microcontrollers (MCUs) and integrated motor drivers are optimizing how robots move, and achieving this goal faces 4 major challenges.

Challenge 1: Increasing safety requirements for human-machine collaboration
In the past, humans and robots needed to be strictly separated for safety reasons, often by placing the robots in cages. Increased automation requires closer human-machine collaboration and interaction. Collaborative robots help improve work efficiency, but require motors that can ensure safe stops, safe speeds, torque and motion control.

Devices such as the C2000™ 32-bit TMS320F28P650DK MCU play a critical role in helping meet security requirements. These devices are certified for functional safety and can integrate safety peripherals for diagnostics, simplifying designs to the International Organization for Standardization (ISO) 10218 standard. On the analog side of the spectrum, smart gate drivers like the DRV8353F can help engineers achieve their safety goals with TÜV SÜD certified technical reports. This support document guides engineers through the design steps required to achieve safe torque shutdown in accordance with the IEC 61800-5-2 standard. Whether it's an MCU or a gate driver, there are certain components that can simplify the design process and enable functionally safe motor systems.

Challenge 2: Reduce weight, simplify wiring and reduce costs through decentralized motor architecture
Motor electronics are moving from control cabinets to being integrated directly into robot joints, which helps reduce weight, simplify wiring and reduce system costs. This trend has prompted component manufacturers to develop solutions that can integrate more functions into smaller integrated circuit packages. Space constraints also require higher power density and power efficiency.

Gallium Nitride FETs such as the LMG3422R050 have integrated gate drivers that can increase power stage efficiency to over 99%, allowing integrated motors to reduce or eliminate the need for heat sinks. Using real-time communication peripherals and an absolute encoder interface, systems using MCUs such as the TMS320F28065 can generate pulse-width modulated signals with picosecond resolution. These features reduce cabling from more than 10 cables per motor to a total of two buses for the entire arm. Using an MCU and GaN FETs in this configuration enables designers to optimize wired connectivity by adding single-pair Ethernet functionality through an Ethernet physical layer transceiver such as the DP83TG721.

Challenge 3: Automating precision motion tasks requires greater precision and accuracy
Product miniaturization has had an impact on the choice of motor (servo, stepper or brushless DC motor) for many applications, and the motor control and position feedback complexity has increased in order to be able to achieve the precise motion required to interact with these small products. Semiconductor innovations make it possible to achieve the higher precision required for product miniaturization. For example, current sensors such as the AMC3306 have a  50µV offset voltage and an integrated power supply. Combining these features into a single package improves the accuracy of the control loop and reduces the overall size of the printed circuit board.

Challenge 4: Optimize power efficiency for battery-powered mobile applications
Rather than just being stationary in one place, robots are becoming mobile, helping to deliver packages autonomously and safely explore terrain. Current and future semiconductors used in sensing, processing and real-time control applications need to balance high performance and power efficiency to ensure reasonable battery life and possible range.

Achieving high power efficiency does not have to be complex, nor does it require complex design approaches using multiple discrete components. For example, a single motor controller like the MCT8316A can efficiently operate small pump and fan motors by reducing the number of power-consuming components in the robot. This highly integrated device includes six metal-oxide-semiconductor field-effect transistors that form a half-bridge power stage for delivering motor current, and a digital core that enables simple ladder motor control without writing code.

What is the future development prospect of motor control?

The robots of the future will be beyond imagination. They can easily complete tasks that seem impossible today - frequently operating in the deepest trenches of the ocean, or venturing into the unknown of space. New designs are likely to incorporate increasingly advanced sensors, as we currently see with lidar and ultrasonic technology. The way we communicate with robots may even change, from the wired robots of the past to more software-oriented solutions today. Increased accessibility enables more reliable control of robots through speech, visual expression, or even just thought. During this evolution, as robotics technology and applications continue to develop, so must the motors required to drive their movements.