Unmanned tractor second prototype

Universal workhorse for ecofarming

Based on experiences with the previous prototype, Hecada team developed 2017 spring and summer next unmanned tractor prototype. The aim was to improve modularity and performance.

The tractor is universal base platform for automating too boring, repeated, time consuming or routinuous operations usually done by humans. Due to hydrostatic drive, the tractor has excellent axle and central differential effect, so it doesn’t harm grass and soil. It is most suitable for using in agriculture and gardening where driving abilities over and between plants is very important. Therefore, its best field of use would be automation of ecological farming where much work has to be done mechanically due to restrictions. Likewise, this tractor is perfect for cutting hay on meadows and many other gardening works.

Optimized design

The new body module is not built on tubular steel frame, instead uses monocoque design to accommodate much more than previously and have better stiffness.

Powerplant is now entirely situated in one body module, leaving the other module free for carrying working equipment. Improved hydraulic station is more compact, doubles the number of valves and implements automatic pressure adjustment. There are possibilities to mount either internal combustion engine, electric motor or hybrid motor. This time the power source is Kohler 2-cylinder 15 kW gasoline engine. For agriculture use, it has some benefits over the electric motor, like non-stop work because there is no battery charging time. In comparison to bike engine on previous prototype, it has much more power to drive the hydraulic pump. Also the wheel hydraulic motors are larger and more effective type. Combined with individual speed lowering drives, wheels have several times more torque.

Tractor body is water resistant up to air inlets in cover. Therefore the access for maintaining the powerplant and control units is very difficult. To solve this problem, the powerplant is mounted on baseplate which is lifted up with pneumatic cylinders, out of the body.

Central linkage between body modules has improved geometry to significantly decrease steering radius and enclose the hydraulic hoses safely inside.

Improved control system

Besides hardware improvements, electronic system is also redesigned. CAN-nodes don’t base on universal evaluation boards, but are designed specially for controlling this tractor. Image processor is now Nvidia TX2 based. In addition to lidars with wider scanning angle, HD stereo cameras are now in use.

Soil sampling

Second prototype is being used for automating the soil sampling process in fields combined with Agronaut sampling management software. Development of soil sampling and storaging mechanism was supported by Pria and the project was carried out in cooperation with Estonian University of Land Sciences. Soil sampling is very important process in soil fertility management. Usually the samples are collected by driving ATV from point to point or using trailer mounted device that is towed by SUV or tractor. Soil sampling itself is very easy action and this repeated routinuous process can be automated with unmanned tractor:

  • Agronaut software is used for planning optimal sampling points GPS-coordinates in field and also sampling queue,
  • tractor is transported near starting point with car trailer and it loads the trip shape file over 4G network,
  • tractor drives through the waypoints, collects the samples, stores them and returns to starting point,
  • container with samples will be taken to laboratory for analyzes.

Sample is taken with hydraulic mechanism: lowering and rising the mechanism, pressing the probe into ground and cleaning it after. The mechanism is turned automatically 90 degrees before driving, so it will not obscure cameras. Simultaneously with taking the sample, it is possible to measure soil compaction and humidity with separate sensors. Inertial acceleration sensor detects probe collision with a stone and sample taking can be tried again a little further.

Electric soil storaging mechanism is inside the body module. The sample is transported inside the body and put to carton box. Coordinate system with stepper motors carries a full box into its slot in container and takes an empty box from there. One container accommodates 140 boxes.

Testing showed that the tractor performance is quite promising. Based on results, we are already designing the next version, which would be easier and less expensive to produce in series. The next version will be again powered by battery and will have compact yet powerful electric powerplant.