Motion control for agricultural machinery and agritech

In short:Agricultural machinery is going electric one function at a time: a modern combine can carry more than a dozen electric linear actuators for spreaders, sieves and chutes, implements talk ISOBUS, and field robots run on battery-powered servo drives. Specify for a 12/24 V supply, IP69K washdown, dust, vibration and cold starts, with safety-related functions assessed to ISO 25119.

Typical requirements

Machinery we specify motion for

• Combine harvesters
• Forage harvesters
• Tractors and implements
• Sprayers and spreaders
• Seedling transplanters
• Agricultural field robots
• Automated farm equipment
• Agriculture and turf equipment subsystems

What agricultural machinery demands from motion components

Farm machinery works outdoors in dust, chaff, mud, rain and fertiliser, is jet-washed at the end of the day, sits in an unheated shed through the winter, and then has to work flat out for a few weeks at harvest. The supply is a 12 or 24 V vehicle battery, and the operator expects to change settings from the cab without climbing down. That combination is why electric actuators have spread across combines and implements, and why agritech robots are built around low-voltage servo drives.

The shift is well documented. LINAK reports up to 13 electric actuators on a New Holland combine, setting the straw spreader discs and adjusting the sieves for hillside harvesting, and argues that electric positioning avoids the leakage risk and the feedback complexity of hydraulics. Thomson lists combine and tractor makers among its actuator customers.

Where each motion component sits

Combines and forage harvesters

A published combine actuator, the LINAK LA36, is rated at 6,800 N, 160 mm/s and 100–1,200 mm stroke, IP66 dynamic and IP69K static. On forage harvesters, BIBUS describes 12 or 24 V spout and chute actuators that adjust crop discharge direction on the move, replacing cable or hydraulic systems, with IP66/IP69K sealing, integrated limit switches and CAN, analogue or switch control. Those figures are a good template for any agricultural actuator enquiry. Our GD Geared Linear Actuator (300–2,000 N across five ratios, −20 to +65 °C) and GT44 (6,000 N push) cover the lighter and mid-range adjustment duties; see linear actuators.

Tractors, implements and ISOBUS

Implements increasingly take their settings from the tractor terminal through ISOBUS, the ISO 11783 network derived from SAE J1939 and running on CAN. The Virtual Terminal (ISO 11783-6) lets one display run implements from several brands, and the Task Controller (ISO 11783-10) exchanges task data with farm management software, with basic, section and geo-based sub-protocols. The AEF, set up in 2008 to fix incompatible interpretations of the standard, runs conformance testing. An actuator rarely talks ISOBUS itself; it talks CAN or analogue to the implement’s ECU.

Sprayers, spreaders and dosing

Sprayers and fertiliser spreaders turn rate commands into motion: valves, section shut-offs, boom height and spreader vane or disc settings. Electric metering drives replace ground-wheel drives so that rate can follow a prescription map through the Task Controller. For these axes the important figures are low-speed smoothness, repeatable position or speed, and resistance to corrosive product. A closed-loop stepper with an IP65 option, such as the CS-M, or a low-voltage servo motor suits metering and section-control axes. Where a sprayer head or spinner rotates continuously and carries sensors, a sealed slip ring such as the Waterproof Slip Ring range (IP64 to IP68) carries power and signals across the axis. Choose stainless or coated hardware, because fertiliser and crop-protection products attack aluminium and plain steel.

Transplanters and field robots

FAULHABER supplied the drives for gripper handling on the Da Ros TP-24 robotic transplanter: brushless motors with integrated feedback, planetary gearheads and an EtherCAT motion controller, compact enough for a 22 mm minimum gripper spacing and 24 grippers. Kollmorgen stresses torque matched to continuous and peak demand, thermal performance over long duty cycles and frameless motors with large bores for field robots. For battery buses, look at low-voltage servo motors such as the ELVM with drives such as the ELD2 (24–70 V DC, up to 60 A continuous). Wheel-hub gearboxes such as the GL/GLS let a drive wheel mount directly on the gearbox housing.

Turf, municipal and other off-road equipment

Mowers, turf machines, street sweepers and other municipal vehicles use the same building blocks: 12/24 V actuators for decks, brushes, hoppers and chutes, and low-voltage servo drives on electric versions. ISO 25119 can also be applied to mobile municipal equipment such as street sweepers, so the same safety approach carries across. The main difference is duty: municipal machines often run every day of the year, so actuator duty cycle and seal life deserve more attention than on a harvest-only machine.

How to specify motion components for agriculture

1. Supply. State 12 or 24 V, the harness length and the cranking dip. Size cables for stall current.
2. Duty cycle. Most DC actuators are rated for intermittent duty, around 10–25%. Continuous closed-loop correction needs a servo actuator or a higher-duty design.
3. Temperature, including storage. Check the published minimum. Some light-duty actuators are rated only to about −5 °C; rugged off-highway designs such as Thomson’s Electrak HD are published at −40 to +85 °C.
4. Ingress and chemicals. IP69K for washing, plus resistance to fertiliser, crop acids and cleaning products. Specify the connector as carefully as the actuator.
5. Feedback and control. Hall, potentiometer or CAN position feedback; decide whether the cab needs to know position or just end-of-stroke.
6. Functional safety. If the function is safety-related, it falls under ISO 25119. The standard defines AgPL but leaves the level to a machine-specific standard or the manufacturer’s risk assessment.
7. EMC. Agricultural machines have their own EMC standard, ISO 14982. Brushed DC actuators and PWM drives both need checking.

Worked example: a sieve adjuster on a 12 V combine

The function needs 1.5 kN worst-case (including chaff build-up), 100 mm stroke, 10 mm/s, moved a few times an hour, on 12 V.

• Mechanical power: 1,500 N × 0.010 m/s = 15 W.
• Electrical power: with an acme screw and gearing at about 35% and motor efficiency around 70% (rule-of-thumb figures), input is about 15 / (0.35 × 0.7) ≈ 61 W, or about 5 A at 12 V. At 10 V during heavy load or a weak battery, about 6 A, and the actuator also slows.
• Margin: choose a rated load of at least 1.5 times the worst case, so a 2–3 kN class actuator. The acme screw holds the sieve against vibration when unpowered.
• Duty: a few moves an hour at 10 s each is well inside a 10% rating.
• Feedback and sealing: potentiometer or Hall feedback so the cab display shows the setting, IP69K static and IP66 dynamic, sealed connector, −30 °C storage.

A 2,000 N, 12 V geared actuator with feedback fits. If the customer later wants automatic adjustment from a grain-loss sensor, duty rises and the choice moves to a higher-duty or servo design.

Typical pitfalls

1. Choosing an indoor-rated actuator because force and stroke match. Temperature and sealing decide life on a farm.
2. Ignoring duty cycle when a function becomes automatic.
3. Unsealed connectors on an IP69K actuator.
4. Optical encoders on robot axes that get muddy.
5. No plan for the safety assessment under ISO 25119 when an axis can move people or tools unexpectedly.

Send us the machine, function, loads, supply and environment, and our specialist engineering and supply partners will propose actuators, motors, drives and feedback to suit.

Standards to have in view

• ISO 25119 series (tractors and machinery for agriculture and forestry: safety-related parts of control systems)
• ISO 11783 series (ISOBUS: serial control and communications data network)
• SAE J1939 (vehicle CAN network)
• ISO 14982 (agricultural and forestry machinery: electromagnetic compatibility)
• ISO 12100 (safety of machinery: risk assessment)
• IEC 60529 and ISO 20653 (IP codes, including IP69K)

Which standards apply depends on the end product and its market. Your engineer will confirm what the component itself needs to meet.