KHEPERA IV

Khepera IV embeds state of the art features.

The Khepera IV is a compact robot designed for any indoor lab application (table, lab floor).

Compact, it requires a small space to operate, even in swarm. With its high flexibility, the Khepera IV robot can be used in almost any application such as navigation, swarm, artificial intelligence, computation, demonstration, etc . Thanks to the KB-250 bus which allows you to stack many different extensions in a few seconds on the top of the robot, providing an unbeatable modularity.

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Product Description

The newest generation of Khepera is bringing with it a whole lot of new features such as embedded  Linux core, color camera, WiFi, Bluetooth, USB Host, accelerometer, gyroscope, microphone, loudspeaker, 3 top RGB LED, improved odometry and precision.

Introduction to Khepera IV

Khepera IV embeds state of the art features

Based on your experience, feedback and requests, the Khepera IV now integrates a powerful Linux core with WiFi, Bluetooth, accelerometer, gyroscope, color camera and a larger battery.

More stable than ever, you can now plug more extensions on the robot. The different sensors precision has also been improved and the odometry is even better than the Khepera III.

Khepera IV Architecture

The Khepera IV architecture provides exceptional modularity. As any K-Team robot, the Khepera IV is using an extension bus system for nearly unlimited configurations.

The robot includes an array of 8 Infrared Sensors for obstacle detection with 4 more for fall avoidance or line following as well as 5 Ultrasonic Sensors for long range object detection. The robot’s motor blocks are using very high quality DC motors for high efficiency and accuracy. The internal battery provides a running time of about 7 hours.

Khepera IV Embedded Linux Support

With its Linux core, the Khepera IV embeds a complete standard Linux Operating System. It provides a well known standard C/C++ environment for application development. Almost any existing library can be easily ported on the Khepera IV, allowing the development of portable embedded algorithms and applications.

The Khepera IV is the new standard tool for robotic experiments and demonstrations such as:

  • Navigation
  • Artificial Intelligence
  • Multi-Agent System
  • Control
  • Collective Behavior
  • Real-Time Programming
  • Advanced Electronics Demonstration

Evaluation of the robot

The performance evaluation of the Khepera IV is available here (courtesy of the DISAL from the EPFL).
We thank the DISAL form the EPFL for this review, especially Soares, Jorge Miguel; Navarro Oiza, Inaki; Martinoli, Alcherio.

SPECIFICATIONS

Main Features

  • Compact
  • Easy to Use
  • Powerful Embedded Computing Power
  • High capacity embedded battery with possibility to add extra capacity
  • Multiple sensor arrays
  • KoreBot-compatible Extension bus
  • High quality and high accuracy DC motors
  • Embedded color camera
  • Internal microphone and loudspeaker
  • Internal WiFi and Bluetooth antennas
  • 3 axis gyroscope and accelerometer

The pack includes

  • The robot including high performance CPU and battery
  • Power supply for recharge the battery
  • USB Cable
  • Documentation

Khepera IV Specifications

ElementsTechnical Information
ProcessorLinux core running on a 800MHz ARM Cortex-A8 Processor with C64x Fixed Point DSP core and additional microcontroller for peripherals management
RAM256 MB
Flash512 MB plus additional 8GB for data
Motion2 DC brushed motors with incremental encoders (roughly 147 pulses per mm of robot motion) and gearbox
SpeedMax 1m/s in openloop and 0.8m/s with Factory default PID speed controller
Min 0.003m/s with Factory default PID speed controller
Sensors8 Infra-red proximity and ambient light sensors with up to 25cm range,
4 Infra-red ground proximity sensors for line following applications and fall avoidance,
5 Ultrasonic sensors with range 25cm to 2 meters,
3-axis accelerometer and 3-axis gyroscope
Audio1x embedded microphone
1x 0.7W speaker (400-20’000Hz)
VideoIntegrated color camera (752×480 pixels, 30FPS)
LED3 programmable RGB LED on top of the robot
AC adapter power9V @ 2.5A
AutonomyApproximately 7 hours.
Additional turrets will reduce battery life.
BatteryEmbedded battery, 7.4V Lithium Polymer, 3400mAh
Communications1x USB 2.0 host (500mA), 1x USB 2.0 device, 802.11 b/g WiFi, Bluetooth 2.0 EDR
Extension BusExpansion modules can be added to the robot using the KB-250 bus.
SizeDiameter: 140 mm
Height: 58 mm
Weight540g
Max. payloadApprox. 2000 g
Ground clearance4 mm. Use only on hard and flat surfaces
Turn radius0cm
Operating temperature0-40°C
Development Environment for Autonomous ApplicationGNU C/C++ compiler, for native on-board applications.
Other languagePython 2.7.9

LINUX OS

Embedded Linux OS

The Khepera IV is running a full standard embedded Linux Operating System. All applications are developped using the embedded Linux environement which provides several major benefits for developpers. A new library, the libkhepera, is also provided to interface applications with all the robot peripherals and extensions.

Standard Linux Kernel
The Linux kernel is known for its stability and efficiency. Applications will rely on a virtually bug free kernel and will be unable to cause system failures.

Filesystem in Flash Memory
The robot supports a real flash filesystem. Applications can read, create and modify files or directories for data logging, configuration files reading, data storage, etc.

Support for most Common Devices using Standard Drivers
Most USB devices are supported by the Khepera using standard Linux drivers.

Support Standard Libraries for Application Development
Application developer can first rely on the standard C libraries, including all the classic utilities of a Posix system. Moreover, almost any library can be ported on the robot, providing a limitless repository for quick application development.

Quick and Easy Installation of New Software Packages using ipkg
The Linux distribution is based on the Familiar distribution for embedded devices. It supports the ipkg package system for installation of new software. New packages can be downloaded from ipkgfind website.

KHEPERA IV EXTENSIONS

Gripper
KoreIOLE
KoreIO
KoreMotorLE
Expansion Turret
External Charger Pack
Laser Range Finder
Indoor global positioning system (Stargazer)

Gripper

The gripper is a turret that can be plugged on the robot. It gives to the Khepera IV the ability to grab and move objects.

Two degrees of freedom for accurate and robust manipulation and transportation of objects of 5cm width and 50g load.

Made from high precision mechanical parts.

ElementsTechnical Information
Max load size5 cm
Max load weight50g
Power supplyBy the robot
Sizeclosed and up: 108mmx115mmx155mm (HxWXL)
Weight600g
SensorsResistivity, arm position, motor current, infrared
FunctionsGrab object, detect object, measure resistivity of the grabbed material
AutocalibrationBuiltin
Khepera IV with K4 gripper
Khepera IV with extension

 

 

Includes:

  • Kh4 Gripper

Requirements:

Software

  • will be included in the new libkhepera library

User Manual

KoreIOLE

The KoreIOLE is a general Input and Output extension board for the Khepera IV. It provides several interfaces for digital I/O, digital power outputs, 10 bit analog inputs. The KoreIOLE can operate in stand-alone mode or communicate with a Khepera IV or any external SPI or I2C master. A CAN bus controller is also included to connect a Khepera IV to any CAN devices.

SMD electronic

The KoreIOLE supports the KB-250 interface. The KB-250 interface is an open standard interface to expand the functionality of a Khepera robot in a easy and fast way. Besides using a full line of off-the-shelf KB-250 modules, developers can also design their own modules. KB-250 modules can be used singularly or stacked together to give the needed functionality. Several KoreIOLE boards can be placed on one stack to allow control of a large number of I/O.


A set of high level commands is provided, to easily interface Khepera programs or for external operations.


ElementsTechnical Information
Digital IO16 x 5V digitial IO that can be independently configured as
– Input
– Ouput
– PWM output
Digital Power Output6 x digital power outputs
– up to 1 Amps per channel
– externaly provided voltage supply
– fuse protected
Analog Input12 x analog inputs
– timestamped 10bit analog to digital converters
– 0-5V input with a 0.005V resolution
InterfaceI2C Interface (400kbps)
KB-250 Male Interface (for communication with the Khepera IV)
KB-250 Female Interface (for stacking)
Dimensions85mm x 57mm

Includes:

  • KoreIOLE board

Requirements:

User Manual

KoreIO

KoreIO is a general Input and Output extension board for Khepera IV. It provides several interfaces to additional digital IO, digital power outputs, 10 bit analog inputs and 8 bits analog outputs. A CAN bus controller is also included to connect a Khepera IV to any CAN devices.

A special PWM ouput mode is available to control standard Servo Motors. The KoreIO board is able to control up to 10 Servo Motors simultaneously, and to provide them with 5V power supply.

SMD electronic

KoreIO board supports standalone usage using a serial or I2C interface and it can be included in a    KB-250 stack as well. The KB-250 interface is an open standard interface to expand the functionality of an existing ARM base platform in a easy and fast way. Besides using a full line of off-the-shelf KB-250 modules, developpers can also design their own modules. KB-250 modules can be used singularly or stacked together to give the needed functionality.


A set of high level commands is provided, to easily interface the Khepera IV programs or for external operations with the libkhepera.


ElementsTechnical Information
Digital IO16 x 5V digitial IO that can be independently configured as
– Input
– Ouput
– PWM output
Digital Power Output6 x digital power outputs
– up to 1 Amps per channel
– externaly provided voltage supply
– fuse protected
Analog Input12 x analog inputs
– timestamped 10bit analog to digital converters
– 0-5V input with a 0.005V resolution
Analog Ouput8 x 8bit analog outputs
– 4.5V to -5V voltage range
– 15 mA drive current per channel
CAN bus ControllerCAN bus controller and transceiver
– 1Mbps data rate
InterfaceK-Net Interface (for communication with Khepera and Koala)
I2C Interface (400kbps)
RS232 Serial Interface (115kbps)
KB-250 Male Interface (for communication with Khepera IV)
KB-250 Female Interface (for stacking)
Dimensions85mm x 57mm

 

Includes:

  • KoreIO board

Requirements:

User Manual

KoreMotorLE

KoreMotorLE provides two DC motor channels. It can drive up to two DC motors using separate PID’s to control position, and speed. The PID control loop is implemented with 32-bit calculations, with a 32-bit position value and a 16-bit velocity value. Current measurement feedback is also available to detect torque and stall conditions for the motors.

KoreMotorLE does not support standalone operation. The board must be connected to a Khepera IV using the KB-250 stack.

SMD electronic

The KoreMotorLE supports the KB-250 interface. The KB-250 interface is an open standard interface to expand the functionality of an existing Khepera robot in a easy and fast way. Besides using a full line of off-the-shelf KB-250 modules, developers can also design their own modules. KB-250 modules can be used singularly or stacked together to give the needed functionality. Several KoreMotorLE boards can be placed on one stack to allow control of a large number of motors.


Features:

  • Control for 2 DC motors with incremental encoders.
  • Motor requirements:
    • 5-28V
    • 25W max
    • 2.5A max continuous
    • 5.0A max peak
  • Control:
    • open or closed loop regulation
    • position, speed and current (torque) control
    • adjustable sampling frequency from 10Hz up to 12kHz
  • One 2A fuse per motor and one common 5A fuse
  • K-Net Interface (for communication with Khepera and Koala)
  • KB-250 Male Interface for communication with Khepera IV
  • KB-250 Female Interface for stacking
 

Includes:

  • KoreMotorLE board

Requirements:

User Manual

Expansion Turret

 

 

The expansion turret can be plugged on the top of the Khepera IV to improve the capabilities of the Khepera IV. This turret will provide many different options to the Robot:
· Laser Range Finder (LRF) connection capability (Hokuyo URG-04LX-UG01)
· StarGazer (indoor global position and bearing) connection capability
· Additional battery for a larger autonomy with the K4 external charger pack
· IOs accessibility

With the expansion turret it is now possible to connect and use on the same Khepera robot a LRF module and a stargazer module at the same time.

The expansion turret give access of different GPIO’s of the Khepera by soldering a wire:

  • – Main ground
  • +3.3V supply output (max 2A)
  • +5V supply output (max 2A)
  • COM3 Tx (ttyS2), GPIO166
  • COM3 Rx (ttyS2), GPIO165
  • Interrupt 1 input, GPIO10
  • Interrupt 2 input, GPIO186
 
  • I2C SCL, GPIO184
  • I2C SDA, GPIO185
  • SPI MISO, GPIO173
  • SPI MOSI, GPIO172
  • SPI CLK, GPIO171
  • SPI CS1, GPIO175
  • PWM1, GPIO144
  • Kh4 battery Voltage
  • COM1 Rx (ttyS0), GPIO151
  • COM1 Tx (ttyS0), GPIO148
 
K4 expansion turret alone
Expansion turret with additional battery inserted in
K4 expansion turret with LRF sensor Hokuyo URG-04LX-UG01
K4 expansion turret with Stargazer module
K4 expansion turret with LRF, Stargazer and additional battery
Left setup on the Khepera IV

Includes:

  • Kh4 expansion turret

Requirements:

Software

  • will be included in the new libkhepera library

User Manual

External Charger Pack

The K4 external charger pack is an option to the expansion board. Composed by two batteries, an external charger and a power supply. It is used to add autonomy to the Khepera IV robot. The additional battery of 3600mAh adds about 5 hours of autonomy to the Khepera IV. It is particulary indicated when you use a Stargazer and / or a LRF module, in order to save the autonomy of the robot.

Another advantage is that you are able to change the additional battery while the nattive battery inside the robot is still powering the robot, making unnecessary to restart your robot and allowing you to run a virtualy unlimited experimen

tation time.

The additional battery is plugged into the expansion board (not included in the K4 external charger pack).

The pack include two additional batteries and the charger which can charge up to 2 batteries in about 4 hours.


 

Here is a brief summary of the gain of autonomy with the additional battery :

SetupAutonomy without additional batteryAutonomy with additional battery
KheperaIV aloneabout 7 hoursabout 12 hours *
KheperaIV with LRFabout 5 hoursabout 8.5 hours *
KheperaIV with StarGazer
about 4 hoursabout 7 hours *
KheperaIV with LRF+StarGazer
about 3 hoursabout 5 hours *
KheperaIV with Gripper
about 4 hoursabout 7.5 hours *
KheperaIV  with Gripper+LRF+StarGazer
about 2.5 hoursabout 4.5 hours *

*Time indicated above are average, depending of the CPU and motor use.

 

Additonal battery (the pack includes two of them)

External charger, it can charge up to two batteries in the same time in about 4 hours.

Includes:

  • Kh4 external charger
  • Powersupply
  • Two Khepera IV batteries

Requirements:

Laser Range Finder

The expansion turret can receive in option a Laser Range Finder module. It is used to do navigation, specially for mapping and localization. A laser inside the sensor is scanning the robot environment, measuring each 0.36 degres the distance from any object at its height.

The model which can be used is the URG-04LX-UG01 from the Hokuyo company. The turret gives the mechanical support for the sensor and the connectivity for it. In option, you can add a battery with the external charger pack in order to save the Khepera IV robot autonomy.

Technical specification of the LRF module:

ElementsTechnical Information
Range20 mm to 5600 mm
Accuracy60 to 1000mm : ±30mm ,
1000 to 4095mm : ±3% of measurement
Angular resolutionapprox. 0.36 degree
Autonomy2 hours
Weight300g
SoftwareLibkorebot
Scanning time100ms / scan

LRF module on the expansion turret

 

Includes:

  • Kh4 expansion turret with the LRF module installed

Requirements:

Software

  • will be included in the new libkhepera library

User Manual

Indoor global positioning system (Stargazer)

The Stargazer is a module allowing the Khepera IV robot to have indoor global position and bearing from passive landmarks marks.

It is used to do navigation, specially for mapping and localization. The module has IR Led’s for lighting landmarks and a camera for capturing the image, which is processed by on-board electronics. It computes position and bearing related to landmarks stuck on the ceiling. It uses the StargazerTM module from Hagisonic co. Ltd.

This a top module. No module can be plugged above this one.

ElementsTechnical Information
Range2.5-3 m of diameter with 1 landmarks (for ceiling height of 2.4 m; can be improved by adding landmarks)
Accuracy3.5 cm / 3 degrees
Measurement time10 times /sec
Autonomy2h30 ; Li-Pol battery
Weight117 g
SoftwareLibkhepera
CompatibilityKhepera IV extensions (KB-250 specifications)
 

Includes:

  • Kh4 expansion turret with the Stargazer module installed

Requirements:

Software

  • will be included in the new libkhepera library

User Manual

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