PRESENTATION ON

Vehicle Operator Safety

The Advantages of Using Electronic Sensors in Off-

road Vehicles

Off-road vehicles are designed to perform onerous tasks in extreme outdoor conditions. In industries such as construction, agriculture and forestry, vehicles must navigate on uneven surfaces while lifting and moving heavy loads. For vehicle operators, the chances of tipping or rolling over are high, and safety is a concern. By installing preventative measures such as electronic sensors to detect the vehicle’s operating condition and alignment, operator safety is increased. This   paper will describe the advantages of using three distinct sensor types in off-road vehicles to improve operator safety.

INTRODUCTION

Picture of off road vehicle

Summary for 2015/16 The provisional figure for the number of workers fatally

injured in 2015/16 is 144, and corresponds to a rate of fatal injury of 0.46 deaths per 100,000 workers.

The figure of 144 worker deaths in 2015/16 is 7% lower than the average for the past five years (155). The latest rate of fatal injury of 0.46 compares to the five-year average rate of 0.52.

The finalised figure for 2014/15 is 142 worker fatalities, and corresponds to a rate of 0.46 deaths per 100,000 workers.

Over the latest 20-year time period there has been a downward trend in the rate of fatal injury, although in recent years this shows signs of levelling off.

There were 67 members of the public fatally injured in accidents connected to work in 2015/16 (excluding incidents relating to railways, and those enforced by the Care Quality Commission).

Fatal injury statistics

 Number and rate of fatal injury to workers 1996/97 – 2015/16

How to prevent vehicle operator injury

To prevent vehicle operator injury, electronic sensors can be used in off-road vehicles to warn the operator if the vehicle or its

load is in danger. These sensor families include tilt sensors, inductive position sensors and pressure sensors. The

technologies behind each sensor family will be examined as well as application examples presented . Environmental exposure is

also a safety factor. As virtual "plants-on-wheels," off-road vehicles are exposed to extreme shock and vibration, harsh

chemicals, dirt and electrical interference. The sensors used on these vehicles must be able to withstand these same extreme

conditions to prevent mechanical damage and downtime.

Types of Sensors .

1.Electrolytic Tilt Sensor 2. Micro Electromechanical Sensor (MEMS) 3. Inductive Position Sensors 4. Inductive Proximity Sensors 5. Pressure Sensors

Tilt Sensors Monitor the Safe Horizontal Alignment of Vehicles

Inductive Position Sensors Monitor the Position of Moving Parts on a Vehicle

micro electromechanical sensing Inductive proximity sensors take advantage

of changes in a resonant circuit c Pressure Sensors Monitor a Vehicles

Hydraulic System

Working of sensors

1.Electrolytic tilt sensing

The first technology is referred to as electrolytic tilt sensing1. Sensors filled with electrically conductive liquid are fitted with two internal measuring cells. By applying an alternating voltage between the cells’ electrodes, current flows through the liquid and generates an electrical field. If the sensor tilts, the fluid surface remains level, so the electrical field changes – as well as the fluid’s level-dependent resistance. The measuring cells monitor any change in the liquid’s conductivity and thus detect angle variations of the X and Y axes with precision. Sensors using this technology are appropriate for platform leveling (narrow tilt angle ±15°) or where high precision (0.025°) and a flexible network connection are advantageous.

Figure 1. Electrolytic tilt sensing technology: measuring cells monitor any change in the liquid’s conductivity to detect angle variations.

Electrolytic sensor :

2.MEMS sensor

The second technology is micro electromechanical sensing (MEMS). A silicon mass is suspended in the sensor body by two resilient beams between two stationary capacitor plates. When the body tilts, the movement is transferred to the beams. The beams deflect to take the inertial forces of the mass. The deflection changes the relative position of the mass between two plates. Because each of the above plates is part of two separate capacitors, the deflection creates a reciprocal change in capacitance in each of the two. Any change in capacitance is proportional to the tilt of the sensor, which then is converted to a change of voltage and transferred as an analog value to the vehicle controller. Sensors incorporating this technology are better suited to applications where a single-axis wide tilt angle (±90°) and lower precision (±1°) are needed. 

MEMS sensing technology

Figure 2. Micro electromechanical sensing (MEMS) technology: When the vehicle tilts, the movement is transferred to the beams that deflect to take the inertial forces of the mass. Any change in capacitance is proportional to the tilt of the sensor.

3. Inductive Position Sensors Monitor the Position of Moving Parts on a Vehicle

Inductive position sensors are designed to detect the position of moving parts on an off-road vehicle. Multiple sensors can be used on one machine to maximize the operation of the vehicle and to protect the vehicle’s operator. For example, a position sensor can be used on an industrial crane’s cable drum to detect the end of its cable, protecting the crane against machine damage. Position sensors can also monitor the rotational speed of a gear, detect the position of a platform, or sense the open- and closed-position of vehicle cab door. The position sensors provide continual feedback on the operating condition of the machine’s moving parts and send this information to the vehicle operator.

Sensing faces made of UV-resistant plastic that won’t break down from exposure to sunlight.

Highly visible LEDs that indicate power and output status that aid in setup and monitoring, especially in direct sunlight.

Stainless steel, zero-leak housings encase and protect the electronics from chemicals and liquid ingress.

Flexible electronic circuitry that resists the effects of shock and vibration. Long sensing ranges that increase the distance between the target and

sensor and reduce the chance of impact and damage to the sensor. Noise-immune technology that enables the sensors to ignore conducted

and radiated electrical noise.

features Position sensors are designed to withstand outdoor conditions and can include the following:

Position sensor :

4. Operating principle of inductive proximity sensors

Inductive proximity sensors take advantage of changes in a resonant circuit caused by eddy current losses in conductive materials. An inductive proximity sensor contains four essential components: a coil of wire wrapped in a ferrite core, an oscillator circuit, an evaluation circuit, and an output circuit. When voltage is applied to the sensor, an oscillating current flows through the coil and radiates an electromagnetic field from the active face of the sensor. This field is directed and shaped by the ferrite core. When an electrical conductor or metal target enters the electromagnetic field, eddy currents are drawn from the oscillator and induced into the target. These eddy currents draw energy from the electromagnetic field. The losses in energy caused by the eddy currents are due to the conductivity and permeability of the target, the distance and position of the target, and the size and shape of the target.  When the metal target is positioned at a precise distance from the active face of the sensor, the energy loss caused by the eddy currents becomes so large that the amplifier cannot output sufficient energy to maintain oscillation and the magnetic field collapses. The breakdown in oscillation is detected by the evaluation circuit, which then changes the state of the output circuit.

Figure 3. An inductive proximity sensor detects all metals with its high-frequency electro-magnetic field.

Inductive sensor :

5. Pressure Sensors Monitor a Vehicles Hydraulic System

The hydraulic system of an off-road vehicle is the heart of the vehicle and is responsible for operating the main controls. Applications such as loading and unloading, transporting, lifting, and processing are achieved through the hydraulic system. Loss in power can result in vehicle downtime and potential injury to the operator. Pressure sensors can continuously monitor a vehicle’s hydraulic system and provide feedback on the system’s operating condition. Pressure sensors today are stainless steel and compact. The base of the sensor incorporates a ceramic sensing element that enables over 100 million switching cycles, withstands pressure spikes, and resists corrosion. The design of the sensing element ensures excellent repeatability and accuracy across the entire operating range. Similar to inductive proximity sensors, electronic components are mounted on flexible film for shock and vibration resistance up to 1000g.

IP69K rating for washdown environments EMC protection (>100 V/m radiated HF). Setpoint, hystersis, delay time and damping

values can be configured to meet specific application requirements.

Additional design features include :