Encoderless safety: drive-integrated safety without an encoder
17 December 2019
What is the goal of functional safety? To minimise the risks posed by technical equipment to humans and the environment. Machine tools, for example, can endanger operators and technicians with tools that rotate at high speeds. Drive technology that ensures the required safety functions without encoders offers the user various advantages, says Mark Checkley of KEB.
The safe operation of machines often requires safety functions to limit speeds, directions of rotation or axis positions. With traditional safety solutions, dangerous operating states are detected and avoided using external safety modules. This increases the complexity of the machine's safety concept. In contrast, drive controllers with integrated safety functions and safety PLCs including certified function blocks are used today, which reduce the wiring effort and simplify the safety concept. In some applications with compact motors or high-frequency spindle motors, encoder mounting is not possible for safe monitoring functions but, as speed monitoring usually depends on encoder signals, new concepts for safety functions without sensors are necessary. In addition to more individual machine concepts, encoderless safety functions in the drive offer cost effective options for simple drive monitoring and there is also the benefit that maintenance and repair costs can be reduced.
Applications where encoderless safety functions offer advantages:
• For harsh environmental conditions that restrict the use of an encoder.
• In cost-intensive applications with encoderless drive control.
• For switching between several motors on one drive controller.
• No need to implement complex mechanical or electrical measures.
Read the full article in the January 2020 issue of DPA.
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