MERLIN: Mechatronic Integrated Devices (MID) in action
A special foot switch, condition monitoring for electric motors and moisture measurement in a confined space: in the it's OWL project MERLIN, Mechatronic Integrated Devices (MID) come into practical use and make it possible to place sensors where it was previously difficult.
MID for the operating room foot switch
Two different example applications are to be processed in the pilot project with the company steute. A tightness measurement is to be integrated into a medical foot switch. The foot switch under consideration is used in surgical procedures. So that the surgeon has his hands free during the operation, medical devices can be controlled with the foot switches. To avoid failure, the foot switch is to be expanded to include a leakage measurement during operation.
The existing base plates were therefore coated with an MID lacquer, making it possible to apply metallic structures. Two different measurement principles, resistive and capacitive, were implemented in initial trials. For this purpose, various structures were developed, produced and put into operation in initial tests. Suitable manufacturing parameters were then used to build a circuit. By means of a C/V converter, a change in capacitance, as caused by a drop of water on the structure, is converted into an output voltage. This voltage change can be evaluated at a microcontroller. Figure 1 shows the capacitive structures and the layout applied to the bottom plate.
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it's OWL Clustermanagement GmbH
Christian Fechtelpeter
it's OWL | Leistungszentrum Engineering Automation
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Sensor for intralogistics
The second application is the integration of an antenna directly into the housing of a sensor for intralogistics. The wireless sensor detects whether small parts containers are located on shelves. A large-dimensioned rocker is used as the actuating element here. An integrated sensor detects the inclination and sends a corresponding signal to the base station via SWave. Receipt of the message is confirmed with an acknowledge. To improve the range and optimize the radiation characteristics, the antenna is to be mounted directly on the inside of the housing. Due to the limited space available, various antenna types were researched and an inverted F antenna was selected. This was simulated and gradually optimized until the desired antenna characteristics were achieved. Figure 2 shows a CAD rendering of the antenna on the inside of the enclosure.
Inverted-F antenna applied to the inner side
Condition monitoring for electric motors
The pilot project with the company Lenze is about a condition monitoring system for electric motors. Defective or worn ball bearings lead to vibrations, which can be detected by an acceleration sensor. The use of CMID technology makes it possible to apply the circuit directly to the metallic housing and thus has an enormous advantage over conventional manufacturing processes. Figure 3 shows the circuit applied to the cover of the motor housing. To avoid the need for additional cables to supply power to the sensors, the power supply is to be provided via the phase voltage. The challenge here is that phase voltages of approx. 400AV must be regulated to 5V. Since no commercial solutions are available for this application, a switched-mode power supply is also being developed as part of this pilot project.
Housing cover of an electric motor with applied CMID circuitry
Moisture measurement in a confined space
The pilot project with contech and Berg Spanntechnik is about rotating unions. Rotary unions are needed to convey a medium (e.g. lubricant or coolant) from the stationary part of a machine to the rotating part. They are used, among other things, in CNC milling machines. Special sealing discs are used for sealing. The fluid pressure is up to 80Bar and the rotating part of the machine rotates at up to 80000 rpm. Due to the high operating pressure, leakage of the sealing discs usually leads to total failure of the machine. An impending leak is usually indicated by the escape of individual drops of liquid. The goal of this pilot project is therefore to detect the escaping liquid drops at an early stage in order to initiate a targeted shutdown of the machine and thus avoid total failure.
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