The customized haptic control circuit consists of following major elements
A. Remote unit
The user has freedom to rotate the neck as well as arm of Virtual Desktop Lamp. The neck and arm movements are provided by X, Y, Z coordinates which change dynamically with neck and arm positions. These coordinates are held within matrix which can be retrieved from the VRML code when user’s intension is to establish control over the object. The basic function of remote unit is to retrieve and control the four parameters like coordinates of X, Y, Z axis and switch status i.e. ON/OFF. Block diagram of simple remote unit is shown in Figure 5.
The block diagram shows only one X, Y, Z pivot arm corresponding to one VRML sphere sensor. It is just a simplified representation of complex system. In actual, there are three pivot arms corresponding to VRML sphere sensors. There should be equal number of X, Y, Z switches corresponding to number of pivots (sphere sensors) used in lamp assembly i.e. number ofsphere sensors and number of switches should match each other. Dedicated switch for each spheresensor will increasecomplexity of circuit. As stated earlier, the virtual desktop lamp has three VRML sphere sensors. Logically, one vertical X, Y, Z point for lamp head which seems to be final result of all partial contribution of all X, Y, Z pivots (sphere sensors) and arm position. Circuit simplification trick can be found in selector switch which will allow user to navigate through different sphere sensors sequentially. For tracking of routine human body movement triaxial accelerometer can be used as a sensor which can responds for x, y and z axes. The movement of these axes can be estimated as velocity and displacement by the person who operates that smartphone [12].
The arrangement of selector switch is as shown in Figure 8. The circuit is equipped with selector switch. Which when operated, it switches to next pivot i.e. VRML sphere sensor. This eliminates independent controllers for each VRML sphere sensor thereby making circuit design simple and easy. This trick has helped to design compact circuit assembly. The circuit is quite small in size and can be operated by battery. It can be fitted on any small box. The movements of box will be reflected on Virtual Desktop Lamp. In other words, it can be claimed that box movements are fully mapped with Virtual Desktop Lamp. The box along with control circuit fitted over hand glove as shown in figure 6.
Once the coordinates are fully mapped with gyroscopic sensor, it is capable of rotating Virtual Desktop Lamp’s neck and arms in all 3600 with hand movement [7].
The logical sequence of operation can be clearly explained by figure 7. It shows the flow chart for process controller. Figure 8 shows modified block diagram of remote unit to achieve compact and simple circuit design. The block diagram shown in Figure 8 indicates that there is selector switch which is used to select pivot / arm among the available sphere sensors one by one sequentially. The values (signals) of X, Y, Z, L (ON/OFF) are then sent accordingly.
Further improvement in remote unit was carried out by removing the machine switches for X, Y, Z values with an Accelerometer Electron Integrated Chip [ADXL SERIES]. This chip gives three values with respect to spin about an axis. An accelerometer can measure the amount of acceleration generated due to gravity in terms of the tilted angle with respect to the earth. For such type of acceleration measurement ADXL335-three axis accelerometer is used. This accelerometer has on board voltage regulator IC and modified analog voltage output. This accelerometer manufactured from different analog devices
To move lamp in all direction, user need either mechanical force which can be generated manually (hand glove) or electronically via motor which will precisely control processing elements like microprocessor or microcontroller. For such controlling arrangement, electronic circuit is designed with main elements shown in Figure 9.
The hardware setup of customized haptic control is as shown in Figure 10. The setup consists of 9-volt battery, 5 Volt regulator, Microcontroller (PIC 16F72/PIC 18F2250), ADXL (335/345) chip, USB to serial Cord, Bluetooth Module and PC/Laptop.
B. GY-61 ADXL335 3 Axis Accelerometer Module
GY-61 DXL335 3-Axis Accelerometer Module is a sensor module having three axis centered on ADXL335 integrated circuit. The ADXL335 is a three axis accelerometer with exceptionally low noise and power consumption. The sensor attached having range of +/-3g. This sensor module can measure the static acceleration of gravity in angle-sensing applications, as well as dynamic acceleration evolving from movement, collision or vibration. As mentioned above the ADXL335 accelerometer works with voltage regulator IC of 3.3V therefore the IC provides the power in between the range of 3.3V to 6V DC. Another model is GY-61whih used for gaming and various mobile devices.
The main elements of circuit are
- Battery/ main supply
- Power supply
- Wi-Fi circuit
- Motor
- Motor driver
- Microprocessor/ Microcontroller
- Switches
- Lamp
- Accelerometer assemblers
Details of each block are as follows: -
1. Battery/ main supply: -
Battery is used to provide power to complete system. Power from main supply can be provided but battery power is recommended in situation of frequent power failure.
2. Power supply (inside circuit board): -
It is used to provide necessary voltage range and regulation to all the units on the board.
3. Wi-Fi unit: -
This unit provide the wireless controlling to the lamp movements from remote place.
4. Motor
5. Motor driver: -
All movements of lamp are provided by motor. For each pivot there will be one motor. For driving these motor electronic circuit is required called as motor driver circuit which is controlled by microprocessor or microcontroller.
For haptic control, VRML script can be used. This script is annotated to the actual model, which in turn controlled by plug- down to MATLAB script. For real time haptic control of VRML model MATLAB script has been used. This script provides access to Bluetooth Modulefor communication with remote unit for accepting commands [6].
Figure 12 gives block diagram which clearly gives the idea about the haptic control of VRML object using customized control. This type of prototype provides testing and verification ofdata before building actual complex haptic control on large scale. There are some problems to control the wheelchair especially for those people who are having nervous system disease. In this paper a solution given by interfacing the conventional joystick with accelerometer. By using two accelerometers the wheelchair can work in the balance conditions which are supported by two DC motors respectively. [10]
C. Control using microcontroller: -
All activities of circuit board or assembly model structure are completely controlled by microprocessor or microcontroller. Following sequence of activity will give an overview of entire controlling activity
- Wi-Fi unit receives commands from remote unit for movement
- Wi-Fi unit pass these signals to motor processor
- Main processor analyzes the received signal from Wi-Fi unit and take appropriate action regarding motor shaft/ action.
D. Mechanical assembly
Mechanical assembly is X, Y, Z plane robot switch with Motor, Wi-Fi, Mechanical pivot etc. Lamp assembly consists of Lamp Cap, Lamp Holder and Wiring System. Switches are used for manual operation (ON/OFF operation) of lamp as usual.
The construction of actual mechanical desktop lamp is as shown in Figure 13. The lamp has several ball joints which allow it to rotate in 3600. The mechanical assembly consist base, two arms and one neck. The base, arms and neck are connected to each other by ball joint which gives 3600 freedom of rotation. The virtual desktop lamp created using VRML code is exact replica of this lamp [9].