KUKA KR C4 compact robot controller

KUKA KR C4 compact robot controller

KUKA KR C4 compact is a compact robot controller developed by KUKA Corporation for small industrial robots. It integrates high-performance control, modular design, and advanced security technology into a 19 inch chassis, suitable for various automation application scenarios. This article is based on the official technical document (Spec KR C4 compact V10), which comprehensively analyzes the system architecture, core components, security mechanisms, technical parameters, and planning and installation points of the controller, providing a detailed technical reference for system integrators, maintenance engineers, and technicians.

Chapter 1 System Overview and Modular Architecture

1.1 Composition of Industrial Robots

A complete KUKA industrial robot system consists of the following components:

Mechanical arm: The mechanical body of a robot, responsible for executing movements.

Robot controller: KR C4 compact control cabinet, realizing motion control, logic processing, and communication.

SmartPAD: A human-computer interaction terminal used for programming, operation, and diagnosis.

Connecting cables: including power cables, data cables, and smartPAD cables.

Software: KUKA system software (KSS) and various process software packages.

Options and attachments: External axes (linear units, positioners), process equipment, etc.

1.2 Overall structure of controller

The KR C4 compact controller adopts a modular design and is mainly divided into two units:

Control Box: Includes control PC, power management, safety logic, and communication interfaces.

Drive Box: Includes servo drive module, braking resistor, and power filtering unit.

This separated design is easy to install and maintain, and supports 19 inch rack installation or independent placement.

Chapter 2 Detailed Explanation of Core Components

2.1 Control PC (KPC)

The control PC is the computational core of the controller, responsible for running KUKA system software (KSS) and Windows operating system, realizing functions such as human-machine interface, program management, motion planning, monitoring, and network communication.

Depending on the hardware version, one of the following motherboards can be used to control the PC:

D3076-K: Provides 4 PCI slots for fieldbus cards, onboard 2 USB 2.0, 4 USB 2.0, DVI-I, and LAN (KONI).

D3236-K: Provides 2 PCI slots, onboard 2 USB 3.0, 4 USB 2.0, DVI-I, and LAN (KONI).

D3445-K: Provides 2 PCI slots, onboard 2 USB 3.0, 4 USB 2.0, DVI-D, DisplayPort, and LAN (KONI), supports external display connection through DP-VGA adapter.

All motherboards are pre configured and tested by KUKA, and users are not allowed to modify hardware configurations on their own, otherwise they will lose their warranty eligibility.

2.2 Small Robot Cabinet Control Unit (CCU_SR)

CCU_SR is the core component inside the control box, consisting of two parts:

CIB_SR（Cabinet Interface Board, Small Robot）： Provide functions such as safe input and output, contactor control, fan monitoring, temperature detection, etc.

PMB_SR (Power Management Board, Small Robot): Responsible for power distribution, battery management, power outage buffering, and load testing.

CCU_SR connects the drive box and RDC through the KUKA controller bus (KCB), and connects the smartPAD and external service devices through the KUKA system bus (KSB). Its main functions include:

Safe input/output (9 safe inputs, 4 floating-point outputs)

Quick measurement input (6 channels)

Power monitoring and battery backup

Internal temperature monitoring

Contactor drive and feedback

2.3 Drive Box

The drive box contains the following key components:

KPP_SR (KUKA Power Pack Small Robot): Provides DC bus voltage and braking energy management.

KSP_SR (KUKA Servo Pack Small Robot): A servo drive module that controls motor movement and braking.

Braking resistor: consumes regenerative energy.

**Mains filter * *: Suppresses conducted interference on power lines.

The drive box communicates with CCU_SR through the KCB bus, receives speed commands, and provides feedback on status information.

2.4 Cooling System

The controller adopts a forced air cooling design, and the control box and the drive box each have two independent fans for cooling. The air inlet is located on the front panel and sides, while the air outlet is located at the rear. It is strictly prohibited to install filter cotton in the ventilation opening, otherwise it will cause an increase in internal temperature and shorten the service life of the equipment.

Chapter 3 Security System Design

3.1 Safety Controller

The safety function of KR C4 compact is implemented by a safety controller integrated into the control PC. It is a software core independent of standard control programs, responsible for:

Cut off the drive power and brake

Monitor the braking ramp and static state

T1 mode speed monitoring (≤ 250 mm/s)

Evaluate safety input signals

Set secure output

The safety controller meets the requirements of ISO 13849-1 performance level d (PL d) and category 3.

3.2 Security Interface

The controller provides two optional security interfaces, but only one can be used simultaneously:

Discrete Safety Interface X11: Connected through a 50 pin Harting connector, it supports dual channel emergency stop, operator protection (safety door), enable switch, safety stop, and other functions. The input uses dynamic test pulses (test output TA_S/TA_S) to periodically detect whether the input circuit has failed.

Ethernet Safety Interface X66: Supports PROFIsafe or CIP Safety protocols, communicates with upper level safety PLCs through standard RJ45 connectors, and can transmit safety input/output, monitoring area selection, tool selection, and other signals.

Both interfaces meet the requirements of SIL2 (IEC 62061) and Cat.3 (EN ISO 13849).

3.3 Overview of Security Features

The built-in safety functions of the controller include:

Operation mode selection (T1, T2, AUT, AUT EXT)

Operator protection (safety door monitoring)

Emergency stop (local and external)

Enable switch (three-level enable)

External security stops 1 and 2

External safety operation stopped (static monitoring)

T1 speed monitoring (250 mm/s)

Safety options (such as SafeOperation) can additionally monitor axis space, Cartesian space, velocity, acceleration, etc

3.4 Performance level and PFH value

The PFH value (hazard failure probability per hour) of KR C4 compact is less than 6.37 × 10 ⁻⁸, meeting the PL d requirement. This value is based on a 20-year service life and requires emergency stop equipment to be tested at least once every 12 months. In multi robot collaborative systems such as RoboTeam, the system integrator needs to evaluate the combined PFH value to ensure that it does not exceed the limit of PL d.

Chapter 4 Technical Parameters

4.1 Basic Parameters

Parameter values

Chassis type 19 inch rack mounted

Color RAL 7016

Maximum number of control axes 6

Weight 33 kg

Protection level IP 20

The average noise level is 54 dB (A)

4.2 Power Connection

Parameter values

Rated voltage 200 V -230 V AC, single-phase or two-phase (neutral grounded)

Voltage tolerance: Rated voltage ± 10%

Power frequency 50 Hz ± 1 Hz or 60 Hz ± 1 Hz

Rated power 2 kVA (see nameplate)

Maximum heat loss of 400 W

External fuse 2 × 16A slow melting (C-type)

4.3 Environmental conditions

Parameter values

Operating temperature+5 ° C to+45 ° C

Storage/transportation temperature (with battery) -25 ° C to+40 ° C

Storage/transportation temperature (without battery) -25 ° C to+70 ° C

Temperature change rate ≤ 1.1 K/min

Humidity level 3k3 (DIN EN 60721-3-3)

No derating for altitudes ≤ 1000 meters; 1000 m -3000 m, 5% reduction per kilometer

4.4 Cable length limit

SmartPAD cable: Use up to two extension cords, with a total length not exceeding 50 meters.

Rotary cable: The cable length difference between each channel of the RDC box shall not exceed 10 meters.

4.5 Battery Maintenance

To prevent deep discharge from damaging the battery, it is necessary to charge it regularly according to the storage temperature:

≤ 20 ° C: Charge once every 9 months

20 ° C to 30 ° C: Charge every 6 months

30 ° C to 40 ° C: Charge every 3 months

Chapter 5 Planning and Installation

5.1 Electromagnetic Compatibility (EMC)

The controller meets the requirements of EN 55011 Class A and is suitable for industrial environments. All external connection cables must use shielded cables and ensure that the shielding layer is connected to the PE busbar over a large area through shielding clamps.

5.2 Installation conditions

The controller can be installed horizontally or vertically, and it is recommended to place it horizontally.

If installed in a 19 inch cabinet, the depth of the cabinet should be at least 700 mm.

A ventilation gap of at least 70 mm must be maintained on both sides.

5.3 Power Connection

The power system must be connected to the neutral grounding point. The randomly attached device connection cable provides two options: with power plug or without power plug. It is strictly prohibited to plug or unplug the X11 connector while it is powered on.

5.4 Example of Safety Interface Wiring

X11 emergency stop circuit wiring: External emergency stop contacts should be connected in series to pins 2 (channel A) and 11 (channel B) of X11, and coordinated with test output pins 1 and 14 to achieve dual channel dynamic detection.

Safety door wiring: The safety door switch contacts are connected to pins 4 (operator protection channel A) and 6 (operator protection channel A confirmation), and an external confirmation button (pins 6 and 37/47) is required to ensure that manual confirmation is necessary to restore automatic operation after the door is closed.

5.5 Startup Mode

The 'startup mode' allows temporary disabling of external protective devices in T1 state for debugging and troubleshooting purposes. After activation, all safety outputs must be forced to logic 0, and the danger zone must be isolated with warning tape. This mode is strictly prohibited for normal operation.

Chapter 6 Operation Mode and Safety Measures

6.1 Operating Mode

Mode description speed limit

T1 manual slow speed ≤ 250 mm/s, enable effective, safety door ineffective

T2 manual fast programming speed, enable effective, safety door ineffective

AUT automatic programming speed, safety door effective, unable to be manually operated

AUT EXT is automatically controlled by the upper level controller, and the safety door is effective

6.2 Stop Response

Stop categories corresponding to different triggering conditions:

Trigger conditions T1/T2 AUT/AUT EXT

Press the start button to release STOP 2-

Press the STOP button and hold down STOP 2

Drive to close STOP 1 STOP 1

Enable switch release safety stop 2-

Enable switch full press/fail safe stop 1-

Emergency Stop Press Safety Stop 1 Safety Stop 1

Safety door open - safety stop 1

Safety controller malfunction, safety stop 0, safety stop 0

6.3 Safety Measures

In manual mode, the operator must always hold the enable switch and maintain a safe distance (recommended 50 cm).

After modifying the program, it must be fully tested in T1 mode first.

Do not operate the robot when any safety function is bypassed or removed.

When multiple operators enter a hazardous area, each person must be equipped with an enabling device.

Chapter 7 Maintenance and Service

7.1 Battery replacement and charging

The battery is used to store location data and complete a controlled shutdown after a power outage. Before the first startup, the X305 plug needs to be connected. Long term storage requires regular charging according to temperature.

7.2 Software and Service Interface

X65: EtherCAT interface, used to connect external EtherCAT slaves.

X69: KUKA Service Interface (KSI), used for laptop diagnostics, WorkVisual configuration, and system updates, without the need to connect to the factory network.

7.3 Technical Support

When obtaining support, the following information is required:

Problem description, frequency, and duration

Robot arm model and serial number

Controller model and serial number

System software version

Diagnostic package KRCDiag

Application type and external axis configuration