SAE J1939 / ISO 11783 Tractor ECU

Lecture 7 Tractor ECUISO 11783 Part 9BAE 5030 - 353

Spring 2009Instructor: Marvin Stone

Biosystems and Agricultural EngineeringOklahoma State University

Feb 18, 2009 1BAE 5030-353

Network Context of the TECU

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ISO 11783 Tractor Electronic Control Unit (TECU)

• TECU Functions– Transfers data and command messages to/ from the tractor

to the implement bus as appropriate for the Tractor ECU’s classification

– Represents the tractor on the implement bus, including access to the Virtual Terminal

– Sends requested tractor information on the implement bus– Parses messages and commands from the implement bus

appropriate for the tractor design – Identifies its classification and message set to all ECUs on

the implement bus on request using a tractor facilities message (see ISO 11783-7).

ISO 11783 TECU Tractor Classification

• Specifies Tractor classes of ISOBUS capability– A Tractor ECU classification informs the operator of a

tractor’s compatibility with implements– Each classification identifies a minimum set of messages

that a tractor shall provide to connected implements on the implement bus

• The set of messages a classified Tractor ECU has to provide depends on the tractor’s features

• The Tractor manufacturer may provide additional messages without providing the complete set of messages of the next higher class of Tractor ECU

Class 1, tractor basic information

• Shall provide following internal tractor measurements– Power management:

• key switch state;• maximum time of tractor power;• maintain power request.

– Speed information:• wheel-based implement speed;• ground-based implement speed;• engine speed: message transmission rate shall be 100 ms.

– Hitch Information:• rear hitch position;• rear implement in-work indication.

– PTO (power take-off) information:• rear PTO output shaft speed;• rear PTO output shaft engagement.

Class 1, tractor basic information - Continued

• Lighting:– left-turn signal lights;– right-turn signal lights;– marker light;– left stop light;– right stop light;– implement rear work light.

• Language-specific parameter storage in tractor ECU, VT or both.

Class 2, enhanced tractor information

• Shall provide all of the class 1 messages and – Time & date,– Wheel & ground based distance & direction, – Rear hitch draft and lower link forces, – Complete set of lighting commands– Auxiliary valve (EHRs) estimated and measured status

messages

Class 3, command from the connected implement

• Shall provide all of the class 1 & 2 messages and – Rear hitch commands, – Rear PTO rpm set-point & engagement commands,– Auxiliary valve (EHRs) command messages,

• An implement or the task controller can request the adjustment of the power source as well as the hitch position

• A Tractor - Implement combination can perform the same as a self-propelled machine

TECU Additional Features

• Interface options to TECU classifications 1 to 3 are:– Option (F) -- Front hitch & Front PTO– Option (N) -- Navigation / location

• TECU shall also provide the following capabilities:– Implement electrical power control– Implement lighting control– Safe mode operation

ISO 11783 TECU Electrical Connections

Hazard Sw

Work Light Sw

ECU_PWR

ECU_GND

PWR

Implement Bus

GND

Key Sw

Tractor ECULight Sw

Implement BusBreakawayConnector

Marker Sw

ISO 11783 TECU “Fall-Back” for Lighting

ImplementLighting ECU

CAN BusTwisted Quad Cable

ECU_PWR

PWR

OverloadProtection

Double PoleNC Relay

Left AmberTurn signal

Right AmberTurn signal

GND GND

ECU_GND

Safe-Mode Operation

• Upon loss of power or communication with the tractor, the implement shall assume a condition of fail-safe operation. The interruption, re-establishment after interruption or fluctuation in any manner whatsoever of the power supply to the implement shall not result in a dangerous situation. Neither shall a fault in the control logic, nor failure or damage to the control circuit, be allowed to lead to danger.

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Safe Mode Requirements

– The implement shall not start unexpectedly.– The implement shall not be prevented from stopping if the

command has already been given.– No part of the implement, or a piece held by the implement,

shall fall or be ejected.– Automatic or manual stopping of any moving part shall be

unimpeded.– The protection devices shall remain fully effective.– Remote-controlled implements shall be designed and

constructed to stop automatically in the event of the driver losing control.

– The operator shall have the ability to override implement-controlled systems.

Feb 9, 2009 BAE 5030-353 13