Design And Implementation Of Automatic Sample Filling System Based On CANopen

The automatic sample filling system is used as an automated experimental device and is widely used in the fields of medicine,chemistry and biology.However,due to the R&D started lately and lack of technology,a series of problems such as low filling efficiency,low accuracy,and cross-contamination are common in our country's automatic sample filling systems.At present,the mainstream automatic sample filling equipment on the market is manufactured by foreign companies.Although the performance is superior,it is expensive.On the other hand,CAN+CANopen is considered to be the most successful bus solution in the field of machine automation.Therefore,combining the two to develop an automatic sample filling system based on CANopen for non-pollution,high efficiency,accurate quantitative transfer of various liquids,has high practical value.Based on the mechanical platform provided by the cooperation company,the thesis completed the design of automatic sample filling system.Through planning system CANopen network,transplanting CANopen open source protocol stack CANFestival,defining object dictionary and registering callback interface,the CANopen network is constructed to provide the basis for the coordinated control of the lower machine parts under the CAN bus.The circuit design and device selection of the main control board,liquid level detection module,motion control module and pump module are used to build the embedded development platform for each module of the lower machine.Designing workflow,state machine scheduling of sample subsystem,cup subsystem,filling subsystem and liquid level detection algorithm to achieve sample feeding,cup feeding and filling operation;designing software of the main control unit of the lower machine to control three subsystems to complete the automatic filling;finally,designing the upper computer software interface and communication protocol to realize human-computer interaction.The main contributions of the thesis are as follows: First for the abnormal problems such as packet loss and blocking that may exist in multi-module communication of the lower machine,the CAN+CANopen bus solution is adopted to guarantee the reliability and stability of the communication.Second for the problems of laser,ultrasonic and capacitive liquid level detection modules that are susceptible to interference and inaccurate detection,the liquid level detection solution based on pressure detection that incorporates the pump motion is adopted,and the corresponding algorithm design is completed,effectively improving the anti-interference ability and accuracy.Third for the problem of slow sequential filling of single needle or double needles,the filling process of simultaneous operation of four needles is designed,which saves the waiting time for absorbing before filling in the traditional method,and effectively improves the filling efficiency.Last for the cross-contamination problem in the steel needle filling,the disposable Tip headpiece is used to connect the needle for filling,which guarantees the sample's non-pollution during the process.After repeated testing,the automatic sample filling system of the project is stable in operation,the relative error of filling is less than 2%,the filling rate is greater than 480 tests/hour,the liquid level detection accuracy is greater than 99.5%,and all performance indicators have achieved the desired goal.