As we venture into the heart of mechanical dynamics, we unravel the workings of the technologically advanced component in machinery - the electromagnetic brake. How does it seamlessly bring motion to a halt and smoothly resume it when needed? In this post, we explain what the electromagnetic brake is and how it works, analyze how it can be applied in robotics and in which situations it is most useful.
What is an electromagnetic brake?
An electromagnetic brake is an advanced braking system designed for precision and controlled motion in mechanical applications. It employs the principles of electromagnetism to enable the motion of an object, while maintaining the stopped state when the power is off thanks to mechanical springs. This fail-safe feature ensures that even in the event of a power failure or intentional shutdown, the system remains in a halted state, preventing unintended movement and contributing to enhanced safety. The electromagnetic force, when applied or removed, becomes the decisive factor in controlling the motion of the mechanical system. Such brakes are widely employed in various industries, including robotics, automotive, and manufacturing, where precise control over motion is crucial for efficient and safe operations.
How does an electromagnetic brake work?
An electromagnetic brake operates in accordance with the principles of electromagnetism, using a carefully planned interaction of magnetic fields and electric currents. The main components of an electromagnetic brake include a field coil, a magnetic core, an armature and a hub which can be attached to a shaft. The brake’s work can be broken down into a few key stages:
Formation of the electromagnetic field: The brake system consists of a coil wound around a magnetic core. When an electrical current flows through this coil, it induces the creation of a magnetic field around the core.
Interaction with the armature: The magnetic field interacts with an integral component called the armature, typically made of ferrous material. Depending on the polarity of the magnetic field, the armature is either attracted or repelled.
Braking action - attraction or repulsion: In one common configuration, when the brake is engaged, the magnetic field attracts the armature, restricting its movement. This attraction creates a force that opposes the motion of the object connected to the brake, resulting in controlled deceleration or a complete stop. Conversely, releasing the brake interrupts the flow of electrical current, ceasing the magnetic field and allowing the armature to move freely. This action permits the unrestricted motion of the connected object, and this is how the MAB Robotics brake works.
Control through electrical modulation: The brake works in only two configurations: it is either on or off. To achieve higher energy efficiency, the engagement of the brake needs to be controlled with an external overexcitement controller. The MD80 has implemented support for the MAB overexcitement module. This makes it possible to apply the brake in solutions requiring increasing the system's energy efficiency.
Should I use a brake?
Braking can be done by a BLDC motor - No need for a brake
While Brushless DC (BLDC) motors do possess inherent braking capabilities, they are primarily designed for smooth and controlled speed changes rather than precise stopping. The braking effect in a BLDC motor is typically achieved through regenerative braking, a process where the motor acts as a generator, converting kinetic energy back into electrical energy.
However, electromagnetic brakes offer a distinct advantage in applications where finer control over the braking process is required. BLDC motors might not provide sufficient precision of movements, especially in scenarios where rapid deceleration or holding torque is crucial. Electromagnetic brakes can be a better choice for applications requiring such control, such as robotics.
Braking when power off
One of the key advantages of electromagnetic brakes is their ability to operate even without power. In the event of a power failure, relying solely on a BLDC motor for braking might pose a significant risk. Electromagnetic brakes act as a fail-safe mechanism, providing immediate and controlled stopping of the system regardless of whether power is available or not. This feature can be critical in applications where safety is paramount, such as medical robotics or industrial automation. The immediate cessation of motion in the event of power loss prevents the system from falling into an uncontrolled state, reducing potential risks and protecting both equipment and personnel.
In safety-critical applications, meeting stringent safety standards is imperative. While BLDC motors offer some level of braking functionality, electromagnetic brakes provide an additional layer of safety. Electromagnetic brakes can be integrated into safety systems, ensuring that in the event of a fault or emergency, the brakes engage promptly, bringing the system to a halt. The ability to meet or exceed safety requirements makes electromagnetic brakes a preferred choice in industries where reliability and risk mitigation are paramount.
The MAB Robotics electromagnetic brake introduction
As MAB Robotics continued to innovate and enhance product offerings, the team integrated a new feature into the MD80 motor controller to better serve the requirements of the company's customers. The feature allows a user to control the electromagnetic brake through the communication interface. Furthermore, MAB introduced a line of MAB SLIM Electromagnetic Brakes to the offer. The MAB SLIM is an ultra thin brake series designed for mobile robotics applications. Brakes are holding when power is off, providing high torque, and low power consumption. The series is compatible with MAB Robotics MD80 motor controller, and has to be used with an overexcitation controller (included in the set). Brakes can operate in 24-48VDC power supply range, and thanks to the modularity you can choose a holding torque from a wide range of 0.06-38 Nm.
Applications for electromagnetic brake
The adaptability and precision of electromagnetic brakes have propelled their integration into a variety of applications across diverse industries. They can be the most commonly seen in:
Robotics and automation - they provide precise control and safety in robotic movements.
Material handling - they facilitate controlled motion in conveyor systems.
Medical equipment - they ensure safety and accuracy in robotic surgical systems.
Elevators and escalators - they act as emergency brakes, ensuring a swift and secure stop in case of unexpected events.
Automotive - they are used for parking and emergency braking in electric vehicles.
Industrial machinery - they enhance safety and efficiency in machinery like CNC machines.
As the demand for new features and safety in robotics continues to grow, electromagnetic brakes stand out as a crucial element in achieving these goals. Their ability to provide controlled and responsive braking, even in the absence of power, makes them a universal solution to be used in various industries. To meet the needs and requirements of the industry MAB Robotics introduced the brakes support from the MD80 motor controller, and added MAB SLIM ultra-thin electromagnetic brakes to the offer. From now, you can integrate a brake into your design, or contact the MAB team to order a customized actuator.
Author: Jakub Bartoszek
Co-founder and CTO of MAB Robotics