Mayr
Medical robotics places high demands on all components used. Whether in radiotherapy systems, surgical assistance systems, or image-guided interventional robots: the focus is not only on process reliability, but on the physical integrity of patients. In an emergency or in the event of a power failure, safety brakes must bring medical robotic systems to a precise and reliable standstill and safely hold moving axes in any position. Patient safety is the top priority.
Medical systems often operate in the immediate vicinity of, or in direct contact with, patients. A multi-leaf collimator in radiotherapy, for example, moves heavy tungsten leaves, often directly above the patient lying on the table. Even an uncontrolled downward movement of just a few centimeters can have serious consequences. The extreme requirements become even clearer in robot-assisted surgical systems. A motion of just a few millimeters can be the difference between a successful surgery and severe harm to the patient. In the event of a power failure, emergency stop, or power interruption, no axis may be allowed to move in an uncontrolled manner.
Precision under extreme conditions
In addition to the direct human contact, which is essentially the norm in medical technology, there are further challenges in medical robotics. Radiotherapy systems, for example, rotate continuously around the patient, with moving masses of 30 kg and more that must be held securely in various spatial orientations, horizontal, vertical, and inclined.
At the same time, extremely short switching times are required in order to reduce stopping distances to an absolute minimum, with consistently high braking performance over the entire service life. There are also requirements regarding smooth running and low noise emissions, since patient confidence in the technology used is also a key success factor.
Fail-safe principle as a basic requirement
For medical robotic systems, often engaged, electromagnetic spring-applied brakes operating on the fail-safe principle are used. These brakes are closed in the de-energized state and generate braking torque via compression springs. Even in the event of a power failure or cable break, the braking torque is reliably available. When the brake is energized, a magnetic field builds up that pulls the armature plate against the spring force, the brake opens.
Suitability as a safety-related component
Users should ensure that the safety brakes employed meet the requirements of Category 1 according to EN ISO 13849-1 as proven components. Reputable manufacturers provide the required safety parameters for this purpose, in particular B10d values for determining the performance level, as well as validation support.
Switching times, braking torque, and friction work
Short switching times reduce stopping distances to a minimum in emergency stop situations. Modern safety brakes are characterized by extremely fast magnetic actuation, typically in the range of a few milliseconds. Specially developed organic friction linings can be used even at high ambient temperatures of up to 120 °C and offer a high, consistent coefficient of friction. They provide stable static and dynamic braking torque with narrow tolerances and enable high permissible friction work.
Compact design without adjustment work
Many medical robotic systems are highly integrated, compact designs. The available installation space for safety brakes is often very limited. At the same time, the brakes may only introduce low additional moments of inertia so as not to negatively affect system dynamics.
Modern safety brakes for medical applications must therefore be extremely compact, have as little weight as possible, and exhibit low moments of inertia. Ideally, no adjustment work is required, in order to minimize potential error sources during installation. In other words, the brake is a tested, ready-to-install component.
Modular system solutions – safety for every scenario
With the ROBA® servostop® series, mayr® offers a comprehensive range of safety brakes specifically adapted to the high demands of robotics, including medical applications. The standard modular system includes:
- Both classic servo brakes with hub and toothed rotor
- Slimline versions
- Hollow-shaft designs
The classic servo brakes in the series are available in very small sizes, but also with braking torques of up to 100 Nm. The brakes are particularly wear-resistant and allow a large number of dynamic braking operations. They can be customized and are integrated directly into servo motors.
ROBA® servostop® Cobot and Lean were developed as particularly slim versions specifically for lightweight constructions. The ROBA® servostop® Cobot features a very large inner diameter and is therefore ideally suited for connection to hollow shafts, a common design in medical systems. This solution stands out with reduced weight, a small installation footprint, low moment of inertia, and excellent no-load running characteristics. It is therefore ideal for integration into medical robot joints.
ROBA® servostop® brakes are tested, ready-to-install complete systems that can be integrated easily and flexibly into a wide variety of medical designs.
100% final inspection and traceability
At mayr®, safety brakes (not only for medical applications) undergo complete 100% final inspection before delivery. All key technical properties (spring force, air gap, pull-in and drop-out voltage) are measured, documented, and uniquely assigned to the serial number. A high-voltage test is also performed. For particularly demanding applications, mayr® carries out advanced tests on request, such as braking torque and switching time measurements.
Intelligent control and monitoring
Modern monitoring modules such as the ROBA® brake-checker® from mayr® release the brake using overexcitation voltage and then reduce to a lower holding voltage once the brake is open. If the voltage is reduced, for example, to one third, energy consumption drops to just one ninth.
Using sensorless monitoring, the system detects the movement of the armature plate via extended analysis of current and voltage and thus knows the current state of the brake. Particularly for very compact brakes with small air gaps, such monitoring used to be difficult to impossible. In addition to monitoring the switching state and critical coil temperature, the ROBA® brake-checker® also provides preventive functional monitoring for wear, functional reserve, and faults.
The power supply and monitoring module operates from the control cabinet, i.e., in a protected environment. Eliminating sensors and cabling in unprotected areas increases reliability and prevents downtime.
Comprehensive engineering support
mayr® provides all necessary data for design and selection: definitions of braking torques, switching times, moments of inertia, friction work during emergency stops, the permissible number of emergency stops, as well as information on mechanical interfaces. Product configurators offer convenient tools for selection and sizing, up to and including approval drawings and CAD files.
In addition, mayr® supports users with safety assessments according to EN ISO 13849, for example, by providing B10d values and validation support.
Conclusion
Medical robotics places the highest demands on safety brakes. Patient safety, precision under extreme conditions, and limited installation space require components that are perfectly tailored to the specific challenges.
Modern safety brakes based on the fail-safe principle, such as mayr®’s ROBA® servostop® series, meet these requirements with compact design, low weight, fast switching times, and high braking performance. Modular system architectures provide flexibility for a wide range of installation scenarios, while intelligent control enables predictive maintenance.
mayr® can draw on more than 20 years of expertise in collaboration with the robotics industry and offers comprehensive engineering support, from design and safety assessment through to validation.
Surgical Robotics Technology
