Abstract: Sowing depth has an important impact on the performance of no-till seeder, it is one of the key factors to ensure the rapid germination. However, the consistency of sowing depth is easily affected by the complex environment of no tillage. The Flex sensor was installed on the inner surface of the gauge wheel at 120° intervals to monitor the pressure exerted by the seeding row unit against ground. The pneumatic spring is used as a down force generator, and its intelligent regulation model is established by Mamdani fuzzy algorithm, which can realize the control of the pressure exerted by the seeding row unit aganst ground and ensure the proper seeding depth.
The working process is simulated based on Simulink, The results show that Mamdani fuzzy model has a good following performace of the pressure change against ground. meet the demand of sowing depth regulation.Experiment results in the field show that, when the working speed is 9 km / h, The control error of the system is 40% lower than that of the passive control, the performance of sowing depth was improved.

Key words: Flex sensor, Mamdani fuzzy model, sowing depth, intelligent adjustment