Many groups are building actuators and exoskeletons without considering the safety standards as from prospective commercially approved products.
The question is: what standards have to be followed for mechanical and electronics design of actuators and respectively exoskeletons ?
Which ones do you use?
For ex: max torque, voltage, current, weight, bending angles, gaps (between the cover and moving parts) and so on.
Hi Felix Hamza Lup , where have you seen an extension of the ISO 13482:2014 to exoskeletons?
A thought-provoking question. I think not a single standard can address all the design aspects of exoskeletons. As Felix mentioned there are some issues that can be addressed by ISO 13482 and its extension. It established safety requirements for personal care robots. It consists of mobile servant robot, physical assistant robot (exoskeleton can fit here, if you consider them as machines), person carrier robot. You can perform risk assessment by using ISO 12100. There is in addition an interesting standard ISO 15066 that can define technical specifications for collaborative robots. There is not an established practice of extending this standard to an exoskeleton yet. But I think, it is a exceptionally interesting standard as it can explain the maximum permissible pressure, forces, stiffness constant, speeds for 29 specific human body parts. You can benchmark these values as starting point of your design while considering safety requirements from 13482, and can find maximum permissible torques, speeds, weight (distribution through contact points), etc. I am certain in the near future there more standards like ISO TC299 (TR2348-1/2), ASTM F48 that will be centered around only exoskeleton technology.
PS: On side note, If you consider the exoskeleton as medical electrical equipment then different set of safety requirements and risk assessment standard like IEC 80601-2-78 and ISO 14971 are relevant.
Thanks for your input! Is 2014 the latest revision of ISO 13482, or is there a more recent one that I am missing?
Hi,
We addressed the safety aspects at various levels in the design of Recupera-Reha exoskeleton.
At the mechanical level, we used mechanical end stops in each actuator to limit the range of motion. Further, we optimized the design of parallel kinematics modules so that the range of motion matches that of the human ROM.
At the electronics level, each drive was equipped with its own power electronics and safety mechanism. The supply voltage and current are continuously monitored and controlled by the FPGA, which permits to implement a configurable firmware-based fuse for safety reasons. In addition, each ACU is protected by a hardware fuse with a rated current of 5 A for the linear leg actuators and 3 A for all other actuators.
At the software level:
1. Low level control: each actuator joint is equipped with FPGA based controller and has its own independent hard and soft safety limits on position, velocity and current levels. The controller becomes very stiff near the soft limits and the joints automatically shut down in case of violation of the hard limits. This safety implementation is decoupled from mid and high level controllers.
2. Mid-level control: each software component has its own safety checks and error handling.
At the interaction level: There are various emergency switches both on the system and outside the system accessible to the user and the therapist.
The detailed description of our system can be found here: https://www.mdpi.com/2076-3417/9/4/626/htm
This is a field in development. Some upcoming standards could be relevant for you, such as: JIS B 8446-2 Safety requirements for personal care robots - Part 2: Low power restraint-type physical assistant robot (Japanese Standard, as extension to ISO 13482), which may be converged into TS/TR in extension to the ISO 13482 over time, as well as the IEC 80601-2-78 for rehabilitation robots.
While I completely agree with Jan regarding the standards, some of you might be interested in data on the fault sensitivity of elastic actuators:
https://www.sciencedirect.com/science/article/abs/pii/S0967066116300193
Hello everyone and thanks again for your inputs to this question. We are getting closer to put our actuator to the market. Here you can find some preliminary pics and tests https://www.smarcos.eu/products/