Development of Instantaneous Braking System for Rotating Members ^†

Abstract

Brakes are essential parts of any system that involves motion. A few seconds are spent applying the brake, accumulating enough force to retard a system. In case of emergency stops, we need an efficient braking system that acts quickly and safely to avoid any mishaps. This work aims to develop a prototype of an instantaneous braking system, which can stop the motion of a rotating member. The operating principle of the device is the electromagnetic actuation of a solenoid. The actuation of a solenoid is simple and instantaneous. As a result, we could achieve immediate braking of a rotating member.

1. Introduction

Brakes are generally mechanical devices that slow down the motion of any rotating member. Energy is absorbed from a moving system by dissipating kinetic energy in the form of frictional energy and heat. The applied brake force involves reduced human effort and acts rapidly for a few seconds [1,2]. To avoid accidents in workshops and roads, an instantaneous braking system is used to stop mechanical machines and vehicles. Most emergency braking systems are equipped with mechanical, hydraulic, pneumatic, or electronic actuated systems. The mechanical braking system powers the hand brake or emergency brake. The braking system applies the brake force on the brake pedal and is carried to the final brake drum or disc rotor by various mechanical linkages like cylindrical rods, fulcrums, and springs [3]. However, wear and tear happen on the brake surfaces. A hydraulic brake transfers pressure from the controlling mechanism to the braking mechanism by using brake fluid (usually glycol ethers or diethylene glycol). However, the hydraulic system is too heavy [4]. An automobile’s pneumatic brake system, also known as a compressed air brake system, applies the necessary pressure to the brake pad to stop the car by pressing pressurized air against a piston. The pneumatic system has a leakage problem. These systems even require human effort, hold more space, and lesser instantaneous when compared to electro-mechanical actuation. Our main objective is that the braking should be instantaneous. The electro-mechanical actuation uses a drum-braking solenoid and is quicker in action [5]. When electricity passes through these wires, this creates a magnetic field in the conductor around which it is wound. This magnetic force is used to attract the nearby material, which is connected to the brake wire. Either an electric current is passed through the wire of the coil to generate a magnetic field, or conversely, an external time-varying magnetic field through the interior of the coil generates an EMF (voltage) in the conductor [6]. This is used to drive and retrieve the brake lever based on the given supply of 12 V DC power. Since it involves only a push button, the system is more compact and instant. Hence, we choose a solenoid actuation for instantaneous braking.

In a nutshell, through literature survey it was found that the actuation methods in conventional braking systems have the following disadvantages: heavy, leakage, slow, and extra manual effort. On the other hand, the disadvantages could be overcome by considering electromagnetic actuation. Hence, our objective is to create an efficient and fast actuated emergency braking system.

2. Construction

2.1. Components

• Mild steel fabricated stand unit
• Electromagnetic plunger unit
• 12 V DC supply
• Wheel with braking unit
• 230 V AC motor
• Bearing
• Connecting wires

2.2. Electromagnetic Plunger Unit

A solenoid is a device that has a conductor wound by wires. When electricity passes through these wires, this creates a magnetic field in the conductor around which it is wound. This magnetic force is used to attract the nearby material. The material will be connected to the brake wire. Either an electric current is passed through the wire of the coil to generate a magnetic field, or conversely, an external time-varying magnetic field through the interior of the coil generates an EMF (voltage) in the conductor. This is used to drive and retrieve the brake lever based on the given supply of 12 V DC power [7].

3. Working Principle

The electromagnetic coils behave as normal coils when there is no supply from the battery. When high voltage is applied using an alternator or from a DC battery supply, normal coils turn into electromagnetic coils. Thus, electromagnetic flux is generated by the coils, which in turn attracts the plunger in the unit which has been connected to the brake lever through the brake wire. Due to this, the brake has been engaged and the wheel stops running, and when the supply has been disconnected, the plunger retracts, which makes the brake release [8].

In our proposed model we have one electromagnetic plunger, wheel, AC motor, and DC battery. The electromagnetic plunger and the DC battery, AC motor, and main power supply are connected through wires. The wheel rotates with the help of an AC motor through the pulley and belt arrangement. Actuating the electromagnetic plunger when the wheel is rotating pulls the brake lever and thus arrests the motion [9].

4. Modeling of Electromagnetic Brake

4.1. Layout of the Model

As described in Figure 1, a wheel is considered as the rotating member, which needs to be stopped with the help of a brake. A stand unit is utilized to mount all the necessary components. An A.C motor is used to rotate the wheel, which is powered by a battery. An electromagnetic plunger is connected to the wheel, so that it can actuate the brakes by accessing the brake drum. An actuator is also placed so that the brake can be applied according to necessity.

4.2. Cad Model

Figure 2 depicts the 3D cad model of the layout, which was designed by the CREO software.

4.3. Working Model

The fabricated model of the instantaneous model is shown in Figure 3. Different views of the fabricated models are shown in Figure 4 and Figure 5.

5. Design Calculations

Since the motor power and full speed rpm of the motor are known, the torque can be calculated.

Motor Power:

$$\mathrm{P} = 186.425 \mathrm{W} = \frac{1}{4}\mathrm{H}\mathrm{P} N_1= 1440 \mathrm{r}\mathrm{p}\mathrm{m} (\mathrm{f}\mathrm{u}\mathrm{l}\mathrm{l} \mathrm{s}\mathrm{p}\mathrm{e}\mathrm{e}\mathrm{d})$$

(1)

Torque:

$$\mathrm{P} = \frac{2\pi NT}{60}$$

(2)

where:

• P = power
• T = Torque
• N = speed in RPM
• T = $\frac{186.425\times 60}{2\times 3.14\times 1440}$ = 1.24 Nm

The transmission ratio between the motor and the wheel:

• $D_1$ = 20 mm = Motor pulley diameter.
• $D_2$ = 235 mm = Wheel pulley diameter.

$$\mathrm{i} = \frac{N_1}{N_2} = \frac{D_2}{D_1} \to \frac{1440}{N_2} = \frac{235}{20}\to N_2 = 122.55 \mathrm{r}\mathrm{p}\mathrm{m}$$

(3)

The no-load velocity of the wheel:

Velocity, V = r × ω

(4)

where:

$$\mathrm{r} = \mathrm{r}\mathrm{a}\mathrm{d}\mathrm{i}\mathrm{u}\mathrm{s} \mathrm{o}\mathrm{f} \mathrm{w}\mathrm{h}\mathrm{e}\mathrm{e}\mathrm{l} = \frac{30.5}{2} = 15.25 \mathrm{c}\mathrm{m}$$

$$\mathsf{\omega } = \frac{2\pi N}{60}$$

(5)

$$\mathrm{V} = \frac{30.5}{2} \times \frac{2\times 3.14\times 1440}{60} = 1.96 \mathrm{m}/\mathrm{s} = u$$

Initial velocity is calculated as above. The final velocity is assumed as zero.

Deceleration:

$$\mathrm{a} = \frac{v-u}{t} \mathrm{m}/{\mathrm{s}}^2 = \frac{0-1.96}{t} \mathrm{m}/{\mathrm{s}}^2$$

(6)

• Final velocity, v = 0
• Initial velocity, u = 1.96 m/s
• Time, t = 0.04 s
• a = $\frac{0-1.96}{0.04}$ = 49 m/${\mathrm{s}}^2$

Brake distance [10]:

$$\mathrm{s} =ut + \frac{1}{2}\mathrm{a}{t}^2 \mathrm{m}$$

(7)

Initial velocity,

• u = 1.96 m/s
• Time, t = 0.04 s
• Acceleration, a = 49 m/${\mathrm{s}}^2$
• s = (1.96* × 0.04) − (0.5 × 49 × ${0.04}^2$)
• s = 0.0392 m = 4 cm

The kinetic energy will be converted to frictional heat loss while applying the brake. Thus, the heat generated from the brake can be calculated as follows,

Heat generated [11]:

$$\mathrm{q} = \frac{1}{2}\mathrm{m} ({v_f}^2 - {v_i}^2) \times \mathrm{k} \mathrm{W}$$

(8)

$$\mathrm{q} = \frac{1}{2} \times 3 (0^2 - {1.96}^2) \times (1.148) = 6.6174 \mathrm{W}$$

where:

• $v_f$ = final velocity
• $v_i$ = initial velocity
• m = mass of wheel
• k = rotational elements inertial factor = [1.03–1.60].

The main aim of this work is to create an instantaneous force that should be able to stop the rotation of a moving system. So, by calculating the solenoid force and the necessary braking force for the dimensions of the prototype, we prove that the braking system is capable of stopping the wheel.

Solenoid force [12]:

$$\mathrm{F} = \frac{{(N\times I)}^2{\mathrm{\mu }}_0\mathrm{A}}{{2g}^2} \mathrm{N}$$

(9)

• No. of turns in coil, N = 1250
• Current, I = 10 Amps
• Permeability constant, ${\mathrm{\mu }}_0$ = 4π $\times {10}^{-7}$ H/m

$$\mathrm{A}\mathrm{r}\mathrm{e}\mathrm{a}, \mathrm{A} = \pi Dl$$

(10)

where:

• Diameter, D = 20 cm
• Length, l = 8 cm
• A = $\pi \ast 20\ast 8$ = 160 $\pi$ ${\mathrm{c}\mathrm{m}}^2$
• F = $\frac{{(1250\times 10)}^{2}4\pi \times {10}^{-7}\times 160\pi \times {10}^{-4}}{{2(0.15}^{2)}}$
• F = 219.3 N

Braking Force:

$$\mathrm{F} = \mathrm{m} \times \mathrm{a}$$

(11)

• Mass, m = 4 Kg
• Deceleration, a = 49 m/${\mathrm{s}}^2$
• F = 4 $\times$ 49 = 196 N
• 219.3 N $>$196 N

We see that ‘Force provided by the solenoid is greater than that of the required braking force’. Hence, the wheel can be stopped using this force.

6. Fabrication Processes

To fabricate a prototype model of a braking system, a suitable stand for the setup was designed. The stand unit was fabricated according to the CAD design, which acts as a support for mounting other equipment. M.S steel rod is used for the stand unit. The M.S channels were cut into the required dimensions and welded together. Finally, grinding was carried out to give a finish to it. After the assembly of the stand unit, the electromagnetic plunger was mounted with the help of L clamps, bolts, and nuts. Then, the wheel unit along with brake drum was mounted in such a way the wheel would be able to rotate freely. The brake wire runs from the brake drum to the solenoid. A switch to actuate the solenoid was also fixed to the stand. Thus, with the help of the motor, the wheel rotates on the mounting. When the brake is applied by actuating the switch, the solenoid pulls the brake wire immediately, which retards the wheel rotation.

7. Conclusions

The working model of the instantaneous braking system was successfully completed. When the wheels started to rotate using an AC motor, the solenoid was actuated using a switch that was powered by a 12 V battery. The wheel stopped in no time. Thus, the desired output was achieved. The solenoid was able to produce a force of 219 N for the given parameters. The braking force required to stop the wheel was 196 N, which is lesser than the solenoid force braking achieved.

The main objective of this project is to make emergency braking easy, instantaneous, compact, and cheap. Thus, using an electromagnetic solenoid has achieved these requirements. The simple operation of the machine requires less skill or manpower to operate. It requires less maintenance than any other type of braking. Thus, we have developed an “INSTANTANEOUS BRAKE SYSTEM”, which helps us to know how to achieve low-cost automation. By using more techniques, they can be modified and developed according to the applications. We conclude this project by saying that such instantaneous braking using solenoid would find a place in emergency braking of modern equipment.