Implementing Functional Safety to off-highway equipment - Agriculture and Forestry machines

Across industries, organizations are required to deliver safe products and create a safe working environment. This can be accomplished by examining potential dangers and designing procedures to address them. While every firm faces risks and obligations as a result of such dangers, a company's actual essence is seen in how they manage these risks.

Before delving into functional safety compliance, it is critical to grasp the context and definitions of the many parts that comprise functional safety. Safety can first be described as the absence of any unacceptable danger that could affect one's health or cause bodily injury. This might be caused directly or indirectly by property or environmental damage. Risk, on the other hand, maybe described as the combination of the degree of harm that can be produced and the likelihood of harm occurring.

Functional Safety can then be defined as the technique of attaining the "absence of unwanted/unreasonable risk produced by risks that occur due to malfunctioning of programmable/electrical/electronic systems". It is an important component of overall safety because it guarantees that a system or piece of equipment responds correctly to the given inputs. Complex technology invaded all industries.

Automotive, agriculture and forestry industries as well are pushed to a fast-paced development to cater to market demands. Off-highway equipment such as tractors and self-propelled ride-on machines used in farming and forestry have come a long way from mechanical systems to complex electronics and software, as in a modern car. These vehicles now come with cutting edge technologies like autonomous driving, electrification, connectivity etc. Manufacturers are facing challenges in developing systems in a short time, low cost and at the same time functionally safe.

Safety regulations:

There are several industry-specific safety regulatory requirements. More regulations will be enacted as the technical complexity of the system increases. Government agencies and the manufacturing industry drive the law. For example, the ISO26262 automotive functional safety standard is not a government regulation standard but is promoted by the manufacturing industry. Similarly, ISO25119 is the agricultural and forestry safety standard. Compliance with standards maintains product trust in the market is a place where various safety systems work together to produce the overall functional safety.

ISO25119- Safety of tractors and machinery used in Agriculture and Forestry

IEC61508 is a fundamental functional safety standard published by The International Electro-Technical Commission. The standard's main objective is to serve as a foundation for additional product and application-specific functional safety standards. ISO25119 is a standard that sits between ISO26262, which is for automobiles, and ISO13849, which is for machines. ISO26262 for automotive and ISO13849 for equipment are both substantially influenced by ISO25119.

ISO 25119 specifies a set of procedures for managing functional safety and regulating product development at all levels, including system, hardware, and software. ISO25119 applies to safety-related components of control systems (SRP/CS) on agricultural and forestry tractors, as well as self-propelled ride-on equipment, mounted, semi-mounted, and trailed agricultural machines. The regulation also applies to municipal equipment such as street sweepers. Only E/E/PES systems include standards and suggestions for "design of systems" with no unjustified risk caused by potential faults in safety-related elements. Hydraulic, mechanical, and pneumatic systems are not covered by the standard.

The standard has 4 parts.

Part 1: General Principles of design and development - In other safety standards, it's referred to as "safety management." This refers to comprehensive safety management, which covers both organizational and project-specific safety.

Part 2: is the concept phase, where the HARA is performed and the safety goals are identified.

Part 3: is the core requirements which talks about how to implement the safety-related functions in system hardware and software.

Part 4: is kind of like a base part, which has supporting processes like configuration management, change management, guidelines for the production, operation, service and decommissioning.

How can one improve the safety of agriculture and forestry machines?

ISO 25119 uses a customer risk-based method to determine hazards, while also allowing for the specification of the goal performance level for the safety-related functions to be executed through E/E/PES safety-related channels. It specifies the requirements for the whole E/E/PES safety life cycle (design, validation, production, operation, maintenance, and decommissioning), which are required for delivering the requisite functional safety for E/E/PES that are connected to performance levels.

For a better understanding of the importance of functional safety, let us discuss the use case of the automated steering system, a vital feature for the tractor in dry-field farming, which was created with a focus on driving precision, installation technique, and operating procedure. Based on ISO25119, the most recent safety standard, a new safety evaluation was developed and used to evaluate the autonomous steering system. Many users in dry-field farming have backed the tractor with an autonomous steering system, and it benefits farmers all over the world. A scarcity of trained human resources is becoming a major issue in agriculture. In this case, GNSS-based (Global Navigation Satellite System) autonomous steering systems are thought to be an effective solution. Along with this, there's the risk of electronics malfunction, which might result in loss of machine control and even a threat to life on the operator.

Malfunction or hazards analysis need to be conducted compliant to the Functional Safety standard to determine the consequences of an electronic failure. Based on this analysis, performance level of the function is achieved (AgPL – Agriculture Performance Level). This performance level is divided into five levels, AgPL a – e, level a being low and e being high.

Implementing Functional Safety

Implementing Functional safety is imperative across every industry, irrespective of the country they are present in. The goal is to use procedures and processes that conform to the compliance requirement. Traceability may be demonstrated from the implemented hardware and software safety measures to the vehicle level hazard that has been handled using the ISO 25119 methodology. Functional Safety engineers must have a thorough understanding of the vehicle system to suggest optimal safety procedures at the system, hardware, and software levels. It's important not to over-engineer the safety measures, since this might influence the cost and performance of electronic systems.

Author: Chanjal Prakash and Dinu Promise