Automatic On-Line Depth Control of Seeding Units Using a Non-Contacting Ultrasonic Sensor

Abstract

Previous investigations on seed placement depth emphasize the importance of proper seeding depth for optimal crop stand and yield. On moist
soils, care should be taken to plant as shallow as possible, but when surface soils are dry and sufficient moisture is not available at lower depths the
planter should seed in a normal depth. To this effect, a non-contacting range sensing and control device for automatic control of seeding depth (DS)
was developed. This system can measure the distance between the soil surface and the frame of a planter where sensor is mounted. In this system
time needed for an acoustic pulse to travel to and from a transducer (fixed to tool-bar) to a reference surface (RS) (attached to planter furrow opener)
is measured and forms a base for this technique. The reference surface plate (RS) is mounted on one side of the runner type furrow opener in such
a way that as the runner increases its working depth the RS is pushed up to the soil surface. The sensor measures the vertical distance between the
transducer and the RS. The measured difference (with no regard to difference size) is transformed into proportionate signal which in turn results
in appropriate operation controllable linear actuator. The actuator then adjusts the tractor hydraulic arms. Indoor and outdoor experiments were
conducted to evaluate the performance of the system under varying conditions. The results showed satisfactory performance of the rig on uneven
soil surfaces and acceptable depth control for the row crop planter.