Poka-yoke is a lean management technique that ensures the existence of the right conditions before the execution of a process step. It is used to prevent the occurrence of defects in the first place. This technique improves the quality of products by preventing, correcting, and drawing attention to any errors as they emerge. There are three types of poka-yoke mistake-prevention techniques including contact methods, motion-stop methods, and fixed-value methods.
The contact methods of mistake-prevention have some sensing device that detects any abnormalities and responds accordingly. The contact methods do not allow a process to start or continue if errors are involved. The second type of mistake prevention is the fixed-value method, preferable in the detection of errors in processes that involve repeated occurrences of the same activity. The third type of poka-yoke is known as a motion-step method, where errors are detected in processes requiring the performance of several different activities in sequence.
The poka-yoke mistake-prevention methods have been widely used in designing medical devices to prevent life-threatening mistakes within the healthcare system. The automatic wheelchair brakes apply the contact method mistake-prevention techniques. These brakes are designed in such a way that the brakes remain engaged when the wheelchair is unoccupied. The wheels turn freely only when a person sits in a wheelchair. The mistake-prevention on these brakes protects patients from hip fractures because of rolling away of wheelchairs during entry.